?面試時(shí)候經(jīng)常會(huì)問的一些問題(不斷補(bǔ)充中)

面試必備基礎(chǔ)題目(雖然不一定常用,?僅用于面試,?面試就是把人搞的都不會(huì)然后砍價(jià),?當(dāng)然您可以講我可以查資料完成,?但是面試的時(shí)候就是沒道理的,?起碼我是經(jīng)常看到這些題).

如何把一段逗號(hào)分割的字符串轉(zhuǎn)換成一個(gè)數(shù)組?
request.getAttribute()?和?request.getParameter()?有何區(qū)別?
response.sendRedirect()?和?forward()?區(qū)別?
<%@include?file="xxx.jsp"%>
和?<jsp:include>?區(qū)別?
List?和?Map?區(qū)別?
Struts?和?Spring?自動(dòng)填充表單參數(shù)到?Bean?的大致原理?
說一下你用的?Spring?+?Hibernate?的方框圖??您都用到了哪些部分??

請(qǐng)用英文簡(jiǎn)單介紹一下自己.

請(qǐng)把?http://tomcat.apache.org/?首頁的這一段話用中文翻譯一下?

?

Apache?Tomcat?is?the?servlet?container?that?is?used?in?the?official?Reference?Implementation?for?the?Java?Servlet?and?JavaServer?Pages?technologies.?The?Java?Servlet?and?JavaServer?Pages?specifications?are?developed?by?Sun?under?the?Java?Community?Process.?

Apache?Tomcat?is?developed?in?an?open?and?participatory?environment?and?released?under?the?Apache?Software?License.?Apache?Tomcat?is?intended?to?be?a?collaboration?of?the?best-of-breed?developers?from?around?the?world.?We?invite?you?to?participate?in?this?open?development?project.?To?learn?more?about?getting?involved,?click?here.?

Apache?Tomcat?powers?numerous?large-scale,?mission-critical?web?applications?across?a?diverse?range?of?industries?and?organizations.?Some?of?these?users?and?their?stories?are?listed?on?the?PoweredBy?wiki?page.

?

try?{
Connection?conn?=?...;
Statement?stmt?=?...;

ResultSet?rs?=?stmt.executeQuery("select?*?from?table1");

while(rs.next())?{

}
}?catch(Exception?ex)?{
}?

這段代碼有什么不足之處??

HTML?的?form?提交之前如何驗(yàn)證數(shù)值不為空??為空的話提示用戶并終止提交??

為什么要用?ORM???和?JDBC?有何不一樣??

Weblogic?的?Server,?Machine,?Node,?Domain?都有何區(qū)別??

簡(jiǎn)要講一下?EJB?的?7?個(gè)?Transaction?Level??

最常見的:?用?JDBC?查詢學(xué)生成績(jī)單,?把主要代碼寫出來.?

Tomcat?5?用?query.jsp?name=中文,?怎么把這個(gè)變量無亂碼的取出來??

finally語句一定會(huì)執(zhí)行么??

前幾天有一個(gè)朋友去面試,被問到這樣一個(gè)問題,如下?

?1?public?class??smallT
?2?{
?3?public?static?void??main(String?args[])
?4?{
?5?????????smallT?t??=?new??smallT();
?6?int??b??=??t.get();
?7?????????System.out.println(b);
?8?????}
?9?public?int??get()
10?{
11?try
12?{
13?return?2?;
14?????????}
15?catch?(Exception?e)
16?{
17?return?3?;
18?????????}
19?finally
20?{
21?return?4?;
22?????????}
23?????}
24?}
25?

輸出：
4
我記得學(xué)習(xí)的時(shí)候說有返回值的方法,執(zhí)行完return語句后就會(huì)停止了;另一方面我還記得在try……catch語句中finally語句也是一定要執(zhí)行的。于是在這里就產(chǎn)生了麻煩。試了一下，發(fā)現(xiàn)果然是執(zhí)行了finally中的值。正好這兩天公司在培訓(xùn)，我便把這個(gè)問題提給java很厲害的一個(gè)講師，他用斷點(diǎn)測(cè)試了一下，說是兩個(gè)值都返回了……
我又改了一小下，在get方法中逐個(gè)添上了輸出信息到控制臺(tái)的語句，發(fā)現(xiàn)居然能執(zhí)行。如下?

?1public?class?test
?2{
?3?public?static?void?main(String?args[])
?4{
?5????????test?t?=?new?test();
?6?int?b?=?t.get();
?7????????System.out.println("Third:?a?=?"+b);
?8????}
?9?public?int?get()
10{
11?try
12{
13?????????System.out.println("First:?a?=?"+2);
14?return?2;
15????????}
16?catch(Exception?e)
17{
18?????????System.out.println(3);
19????????}
20?finally
21{
22????????????System.out.println("Second:?a?=?"+4);
23?return?4;
24????????}
25????}
26}
27

輸出：
First:?a?=?2
Second:?a?=?4
Third:?a?=?4
可這明明是一個(gè)需要返回一個(gè)int整數(shù)的方法啊。?

一道面試題目?

一個(gè)整數(shù)，大于0，不用循環(huán)和本地變量，按照n，2n，4n，8n的順序遞增，當(dāng)值大于5000時(shí)，把值按照指定順序輸出來。
例：n=1237
則輸出為：
1237，
2474，
4948，
9896，
9896，
4948，
2474，
1237，?

美資軟件公司JAVA工程師電話面試題目?

1.?Talk?about?overriding,?overloading.
2.?Talk?about?JAVA?design?patterns?you?known.
3.?Talk?about?the?difference?between?LinkList,?ArrayList?and?Victor.
4.?Talk?about?the?difference?between?an?Abstract?class?and?an?Interface.
5.?Class?a?=?new?Class();?Class?b?=?new?Class();
?if(a?==?b)?returns?true?or?false,?why?
6.?Why?we?use?StringBuffer?when?concatenating?strings?
7.?Try?to?explain?Singleton?to?us??Is?it?thread?safe??If?no,?how?to?make?it?thread?safe?
8.?Try?to?explain?Ioc?
9.?How?to?set?many-to-many?relationship?in?Hibernate?
10.?Talk?about?the?difference?between?INNER?JOIN?and?LFET?JOIN.
11.?Why?we?use?index?in?database??How?many?indexes?is?the?maximum?in?one?table?as?your?suggestion?
12.?When?‘Final’?is?used?in?class,?method?and?property,?what?dose?it?mean?
13.?Do?you?have?any?experience?on?XML??Talk?about?any?XML?tool?you?used?,e.g.?JAXB,?JAXG.
14.?Do?you?have?any?experience?on?Linux?
15.?In?OOD?what?is?the?reason?when?you?create?a?Sequence?diagram??

補(bǔ)一個(gè)內(nèi)部培訓(xùn)用的?PPT:??SQL?Tuning?in?Sybase.zip?17KB,?英文,?Sybase?調(diào)優(yōu),?大部分道理是通用的.

數(shù)據(jù)庫三范式是什么??別看問題簡(jiǎn)單,?我也經(jīng)常答不上來被面試的人寫上數(shù)據(jù)庫不行.

還有就是?Sun?Java?認(rèn)證時(shí)候會(huì)考的一些英文選擇題,?填空題,?模擬題也成.

赴港JAVA開發(fā)工程師的面試題目?

?

也是上個(gè)星期五的上午，按照與獵頭的約定，接受了香港某軟件供應(yīng)商的面試。工作是分析程序員，需赴港工作，以下是面試過程以及題目（大概記下了90%），記下來與大家分享。
第一部分：例行公事的英文自我介紹；
以下部分必須以粵語回答，本人非廣東人，粵語會(huì)講，但是不標(biāo)準(zhǔn)。
第二部分：項(xiàng)目經(jīng)驗(yàn)介紹，著重介紹項(xiàng)目背景，開發(fā)流程以及本人在項(xiàng)目開發(fā)過程中的角色；
第三部分：面試官根據(jù)簡(jiǎn)歷提問：
(1)說出Abstract?class與interface的不同？
(2)Oracle中如何進(jìn)行錯(cuò)誤處理？如果用戶反應(yīng)速度慢，你如何著手解決問題？
(3)圖畫板上列了兩個(gè)table,問查詢結(jié)果，主要是考inner?join與left?join的。
(4)union和union?all有什么不同?
(5)你用什么軟件做設(shè)計(jì)？
(6)是否用過Websphere？
(7)iBatis與Hibernate有什么不同?
(8)談?wù)凷truts中的Action?servlet。
(9)是否開發(fā)過IBM?portal項(xiàng)目。
(10)是否介意加班?
(11)如果你去香港工作，你認(rèn)為你最大的困難是什么?
第四部分：筆試，三個(gè)英文考試題目選一個(gè)作答，內(nèi)容都是寫一份email。
出來后問了獵頭，他說最遲一個(gè)星期內(nèi)就有結(jié)果。
結(jié)果，晚上就接到電話說通過了，并收到了合同和赴港申請(qǐng)的電子文件。工作地點(diǎn)是九龍，月薪18K（中等偏低），合同期一年。獵頭催我盡快簽合同，然后他們馬上就去辦工作簽證。
猶豫ing。

每個(gè)JAVA初學(xué)者應(yīng)該知道的問題?

對(duì)于這個(gè)系列里的問題，每個(gè)學(xué)Java的人都應(yīng)該搞懂。當(dāng)然，如果只是學(xué)Java玩玩就無所謂了。如果你認(rèn)為自己已經(jīng)超越初學(xué)者了，卻不很懂這些問題，請(qǐng)將你自己重歸初學(xué)者行列。內(nèi)容均來自于CSDN的經(jīng)典老貼。
問題一：我聲明了什么！
String?s?=?"Hello?world!";
許多人都做過這樣的事情，但是，我們到底聲明了什么？回答通常是：一個(gè)String，內(nèi)容是“Hello?world!”。這樣模糊的回答通常是概念不清的根源。如果要準(zhǔn)確的回答，一半的人大概會(huì)回答錯(cuò)誤。
這個(gè)語句聲明的是一個(gè)指向?qū)ο蟮囊?#xff0c;名為“s”，可以指向類型為String的任何對(duì)象，目前指向"Hello?world!"這個(gè)String類型的對(duì)象。這就是真正發(fā)生的事情。我們并沒有聲明一個(gè)String對(duì)象，我們只是聲明了一個(gè)只能指向String對(duì)象的引用變量。所以，如果在剛才那句語句后面，如果再運(yùn)行一句：
String?string?=?s;
我們是聲明了另外一個(gè)只能指向String對(duì)象的引用，名為string，并沒有第二個(gè)對(duì)象產(chǎn)生，string還是指向原來那個(gè)對(duì)象，也就是，和s指向同一個(gè)對(duì)象。
問題二："=="和equals方法究竟有什么區(qū)別？
==操作符專門用來比較變量的值是否相等。比較好理解的一點(diǎn)是：
int?a=10;
int?b=10;
則a==b將是true。
但不好理解的地方是：
String?a=new?String("foo");
String?b=new?String("foo");
則a==b將返回false。
根據(jù)前一帖說過，對(duì)象變量其實(shí)是一個(gè)引用，它們的值是指向?qū)ο笏诘膬?nèi)存地址，而不是對(duì)象本身。a和b都使用了new操作符，意味著將在內(nèi)存中產(chǎn)生兩個(gè)內(nèi)容為"foo"的字符串，既然是“兩個(gè)”，它們自然位于不同的內(nèi)存地址。a和b的值其實(shí)是兩個(gè)不同的內(nèi)存地址的值，所以使用"=="操作符，結(jié)果會(huì)是?false。誠(chéng)然，a和b所指的對(duì)象，它們的內(nèi)容都是"foo"，應(yīng)該是“相等”，但是==操作符并不涉及到對(duì)象內(nèi)容的比較。
對(duì)象內(nèi)容的比較，正是equals方法做的事。
看一下Object對(duì)象的equals方法是如何實(shí)現(xiàn)的：
boolean?equals(Object?o){
return?this==o;
}
Object?對(duì)象默認(rèn)使用了==操作符。所以如果你自創(chuàng)的類沒有覆蓋equals方法，那你的類使用equals和使用==會(huì)得到同樣的結(jié)果。同樣也可以看出，?Object的equals方法沒有達(dá)到equals方法應(yīng)該達(dá)到的目標(biāo)：比較兩個(gè)對(duì)象內(nèi)容是否相等。因?yàn)榇鸢笐?yīng)該由類的創(chuàng)建者決定，所以O(shè)bject把這個(gè)任務(wù)留給了類的創(chuàng)建者。
看一下一個(gè)極端的類：
Class?Monster{
private?String?content;
...
boolean?equals(Object?another){?return?true;}
}
我覆蓋了equals方法。這個(gè)實(shí)現(xiàn)會(huì)導(dǎo)致無論Monster實(shí)例內(nèi)容如何，它們之間的比較永遠(yuǎn)返回true。
所以當(dāng)你是用equals方法判斷對(duì)象的內(nèi)容是否相等，請(qǐng)不要想當(dāng)然。因?yàn)榭赡苣阏J(rèn)為相等，而這個(gè)類的作者不這樣認(rèn)為，而類的equals方法的實(shí)現(xiàn)是由他掌握的。如果你需要使用equals方法，或者使用任何基于散列碼的集合（HashSet,HashMap,HashTable），請(qǐng)察看一下?java?doc以確認(rèn)這個(gè)類的equals邏輯是如何實(shí)現(xiàn)的。
問題三：String到底變了沒有？
沒有。因?yàn)镾tring被設(shè)計(jì)成不可變(immutable)類，所以它的所有對(duì)象都是不可變對(duì)象。請(qǐng)看下列代碼：
String?s?=?"Hello";
s?=?s?+?"?world!";
s?所指向的對(duì)象是否改變了呢？從本系列第一篇的結(jié)論很容易導(dǎo)出這個(gè)結(jié)論。我們來看看發(fā)生了什么事情。在這段代碼中，s原先指向一個(gè)String對(duì)象，內(nèi)容是?"Hello"，然后我們對(duì)s進(jìn)行了+操作，那么s所指向的那個(gè)對(duì)象是否發(fā)生了改變呢？答案是沒有。這時(shí)，s不指向原來那個(gè)對(duì)象了，而指向了另一個(gè)?String對(duì)象，內(nèi)容為"Hello?world!"，原來那個(gè)對(duì)象還存在于內(nèi)存之中，只是s這個(gè)引用變量不再指向它了。
通過上面的說明，我們很容易導(dǎo)出另一個(gè)結(jié)論，如果經(jīng)常對(duì)字符串進(jìn)行各種各樣的修改，或者說，不可預(yù)見的修改，那么使用String來代表字符串的話會(huì)引起很大的內(nèi)存開銷。因?yàn)?String對(duì)象建立之后不能再改變，所以對(duì)于每一個(gè)不同的字符串，都需要一個(gè)String對(duì)象來表示。這時(shí)，應(yīng)該考慮使用StringBuffer類，它允許修改，而不是每個(gè)不同的字符串都要生成一個(gè)新的對(duì)象。并且，這兩種類的對(duì)象轉(zhuǎn)換十分容易。
同時(shí)，我們還可以知道，如果要使用內(nèi)容相同的字符串，不必每次都new一個(gè)String。例如我們要在構(gòu)造器中對(duì)一個(gè)名叫s的String引用變量進(jìn)行初始化，把它設(shè)置為初始值，應(yīng)當(dāng)這樣做：
public?class?Demo?{
private?String?s;
...
public?Demo?{
s?=?"Initial?Value";
}
...
}
而非
s?=?new?String("Initial?Value");
后者每次都會(huì)調(diào)用構(gòu)造器，生成新對(duì)象，性能低下且內(nèi)存開銷大，并且沒有意義，因?yàn)镾tring對(duì)象不可改變，所以對(duì)于內(nèi)容相同的字符串，只要一個(gè)String對(duì)象來表示就可以了。也就說，多次調(diào)用上面的構(gòu)造器創(chuàng)建多個(gè)對(duì)象，他們的String類型屬性s都指向同一個(gè)對(duì)象。
上面的結(jié)論還基于這樣一個(gè)事實(shí)：對(duì)于字符串常量，如果內(nèi)容相同，Java認(rèn)為它們代表同一個(gè)String對(duì)象。而用關(guān)鍵字new調(diào)用構(gòu)造器，總是會(huì)創(chuàng)建一個(gè)新的對(duì)象，無論內(nèi)容是否相同。
至于為什么要把String類設(shè)計(jì)成不可變類，是它的用途決定的。其實(shí)不只String，很多Java標(biāo)準(zhǔn)類庫中的類都是不可變的。在開發(fā)一個(gè)系統(tǒng)的時(shí)候，我們有時(shí)候也需要設(shè)計(jì)不可變類，來傳遞一組相關(guān)的值，這也是面向?qū)ο笏枷氲捏w現(xiàn)。不可變類有一些優(yōu)點(diǎn)，比如因?yàn)樗膶?duì)象是只讀的，所以多線程并發(fā)訪問也不會(huì)有任何問題。當(dāng)然也有一些缺點(diǎn)，比如每個(gè)不同的狀態(tài)都要一個(gè)對(duì)象來代表，可能會(huì)造成性能上的問題。所以Java標(biāo)準(zhǔn)類庫還提供了一個(gè)可變版本，即?StringBuffer。
問題四：final關(guān)鍵字到底修飾了什么？
final使得被修飾的變量"不變"，但是由于對(duì)象型變量的本質(zhì)是“引用”，使得“不變”也有了兩種含義：引用本身的不變，和引用指向的對(duì)象不變。
引用本身的不變：
final?StringBuffer?a=new?StringBuffer("immutable");
final?StringBuffer?b=new?StringBuffer("not?immutable");
a=b;//編譯期錯(cuò)誤
引用指向的對(duì)象不變：
final?StringBuffer?a=new?StringBuffer("immutable");
a.append("?broken!");?//編譯通過
可見，final只對(duì)引用的“值”(也即它所指向的那個(gè)對(duì)象的內(nèi)存地址)有效，它迫使引用只能指向初始指向的那個(gè)對(duì)象，改變它的指向會(huì)導(dǎo)致編譯期錯(cuò)誤。至于它所指向的對(duì)象的變化，final是不負(fù)責(zé)的。這很類似==操作符：==操作符只負(fù)責(zé)引用的“值”相等，至于這個(gè)地址所指向的對(duì)象內(nèi)容是否相等，==操作符是不管的。
理解final問題有很重要的含義。許多程序漏洞都基于此----final只能保證引用永遠(yuǎn)指向固定對(duì)象，不能保證那個(gè)對(duì)象的狀態(tài)不變。在多線程的操作中,一個(gè)對(duì)象會(huì)被多個(gè)線程共享或修改，一個(gè)線程對(duì)對(duì)象無意識(shí)的修改可能會(huì)導(dǎo)致另一個(gè)使用此對(duì)象的線程崩潰。一個(gè)錯(cuò)誤的解決方法就是在此對(duì)象新建的時(shí)候把它聲明為final，意圖使得它“永遠(yuǎn)不變”。其實(shí)那是徒勞的。
問題五：到底要怎么樣初始化！
本問題討論變量的初始化，所以先來看一下Java中有哪些種類的變量。
1.?類的屬性，或者叫值域
2.?方法里的局部變量
3.?方法的參數(shù)
對(duì)于第一種變量，Java虛擬機(jī)會(huì)自動(dòng)進(jìn)行初始化。如果給出了初始值，則初始化為該初始值。如果沒有給出，則把它初始化為該類型變量的默認(rèn)初始值。
int類型變量默認(rèn)初始值為0
float類型變量默認(rèn)初始值為0.0f
double類型變量默認(rèn)初始值為0.0
boolean類型變量默認(rèn)初始值為false
char類型變量默認(rèn)初始值為0(ASCII碼)
long類型變量默認(rèn)初始值為0
所有對(duì)象引用類型變量默認(rèn)初始值為null，即不指向任何對(duì)象。注意數(shù)組本身也是對(duì)象，所以沒有初始化的數(shù)組引用在自動(dòng)初始化后其值也是null。
對(duì)于兩種不同的類屬性，static屬性與instance屬性，初始化的時(shí)機(jī)是不同的。instance屬性在創(chuàng)建實(shí)例的時(shí)候初始化，static屬性在類加載，也就是第一次用到這個(gè)類的時(shí)候初始化，對(duì)于后來的實(shí)例的創(chuàng)建，不再次進(jìn)行初始化。這個(gè)問題會(huì)在以后的系列中進(jìn)行詳細(xì)討論。
對(duì)于第二種變量，必須明確地進(jìn)行初始化。如果再?zèng)]有初始化之前就試圖使用它，編譯器會(huì)抗議。如果初始化的語句在try塊中或if塊中，也必須要讓它在第一次使用前一定能夠得到賦值。也就是說，把初始化語句放在只有if塊的條件判斷語句中編譯器也會(huì)抗議，因?yàn)閳?zhí)行的時(shí)候可能不符合if后面的判斷條件，如此一來初始化語句就不會(huì)被執(zhí)行了，這就違反了局部變量使用前必須初始化的規(guī)定。但如果在else塊中也有初始化語句，就可以通過編譯，因?yàn)闊o論如何，總有至少一條初始化語句會(huì)被執(zhí)行，不會(huì)發(fā)生使用前未被初始化的事情。對(duì)于try-catch也是一樣，如果只有在try塊里才有初始化語句，編譯部通過。如果在?catch或finally里也有，則可以通過編譯。總之，要保證局部變量在使用之前一定被初始化了。所以，一個(gè)好的做法是在聲明他們的時(shí)候就初始化他們，如果不知道要出事化成什么值好，就用上面的默認(rèn)值吧！
其實(shí)第三種變量和第二種本質(zhì)上是一樣的，都是方法中的局部變量。只不過作為參數(shù)，肯定是被初始化過的，傳入的值就是初始值，所以不需要初始化。
問題六：instanceof是什么東東？
instanceof是Java的一個(gè)二元操作符，和==，>，<是同一類東東。由于它是由字母組成的，所以也是Java的保留關(guān)鍵字。它的作用是測(cè)試它左邊的對(duì)象是否是它右邊的類的實(shí)例，返回boolean類型的數(shù)據(jù)。舉個(gè)例子：
String?s?=?"I?AM?an?Object!";
boolean?isObject?=?s?instanceof?Object;
我們聲明了一個(gè)String對(duì)象引用，指向一個(gè)String對(duì)象，然后用instancof來測(cè)試它所指向的對(duì)象是否是Object類的一個(gè)實(shí)例，顯然，這是真的，所以返回true，也就是isObject的值為True。
instanceof有一些用處。比如我們寫了一個(gè)處理賬單的系統(tǒng)，其中有這樣三個(gè)類：
public?class?Bill?{//省略細(xì)節(jié)}
public?class?PhoneBill?extends?Bill?{//省略細(xì)節(jié)}
public?class?GasBill?extends?Bill?{//省略細(xì)節(jié)}
在處理程序里有一個(gè)方法，接受一個(gè)Bill類型的對(duì)象，計(jì)算金額。假設(shè)兩種賬單計(jì)算方法不同，而傳入的Bill對(duì)象可能是兩種中的任何一種，所以要用instanceof來判斷：
public?double?calculate(Bill?bill)?{
if?(bill?instanceof?PhoneBill)?{
//計(jì)算電話賬單
}
if?(bill?instanceof?GasBill)?{
//計(jì)算燃?xì)赓~單
}
...
}
這樣就可以用一個(gè)方法處理兩種子類。
然而，這種做法通常被認(rèn)為是沒有好好利用面向?qū)ο笾械亩鄳B(tài)性。其實(shí)上面的功能要求用方法重載完全可以實(shí)現(xiàn)，這是面向?qū)ο笞兂蓱?yīng)有的做法，避免回到結(jié)構(gòu)化編程模式。只要提供兩個(gè)名字和返回值都相同，接受參數(shù)類型不同的方法就可以了：
public?double?calculate(PhoneBill?bill)?{
//計(jì)算電話賬單
}
public?double?calculate(GasBill?bill)?{
//計(jì)算燃?xì)赓~單
}
所以，使用instanceof在絕大多數(shù)情況下并不是推薦的做法，應(yīng)當(dāng)好好利用多態(tài)。

BeanSoft?參加過的一次面試:

?

2004年8月18日?星期三?〖農(nóng)歷?甲申?猴年?七月初三〗?

筆試題目
1.?寫出常用的?Linux?命令
a)?列出當(dāng)前目錄
b)?列出所有系統(tǒng)變量
c)?重命名文件
d)?etc...?記不住了.?

2.?Write?a?Java?application?use?the?Singleton?pattern,?it?should?have?one?instance?per?class.?It?should?have?two?integer?variable,?one?is?count,?on?is?inita.?There?should?be?two?methods?in?this?class,?and?the?method?should?be?thread?safely?in?multi-thread?environment.
a)?a?count()?method,?after?each?call?the?count?should?be?added?on?by?1;
b)?a?reset()?method,?after?each?call?the?count?should?be?set?to?the?value?of?inita.?

3.?Write?a?JavaBean?and?a?JSP?file.?The?page?should?output?a?date?string?in?this?pattern?"今天是2004年8月15日上午10:00",?the?value?is?taken?from?the?bean.?

4.?以下三個(gè)題目,?任選其一或多個(gè):
1)?忘了...,?是關(guān)于?Java?的.
2)?寫一個(gè)應(yīng)用程序,?讀出?STUDENT?表中的數(shù)據(jù)并打印出所有名稱.?數(shù)據(jù)庫系統(tǒng)任選.
3)?寫一個(gè)?Servlet,?讀取名為?url?的參數(shù),?并連接到此字符串指定的地址上,?讀取所有內(nèi)容后顯示給客戶.?

5.?6.?7.?都是關(guān)于?SQL?的,?例如?SELECT,?UPDATE,?DELETE?之類的,?還有的有子查詢.?數(shù)據(jù)庫系統(tǒng)沒有限制.?

8.?Write?a?html?file,?it?shoud?has?follow?functions:
1)?check?whether?the?user's?name?is?empty;
2)?the?email?address?should?has?a?'@';
3)?telephone?number?must?be?'1'-'9',?'-',?'?'(space).
Page?picture:
Please?input?your?name:
[____________________]?[Check?input]
Please?input?your?address:
[abc@________________]?[Check?input]
Please?input?your?telephone?number:
[____123a____________]?[Check?input]?

Java?面試題及其答案?

前段時(shí)間因?yàn)橐獏⒓右粋€(gè)筆試，在準(zhǔn)備期間在網(wǎng)上找到了兩條關(guān)于筆試題目的文章，其中一篇為<<有感:應(yīng)聘Java筆試時(shí)可能出現(xiàn)問題>>，還有一篇忘了名字，讀后深受啟發(fā)。?
在尋找這些答案的過程中，我將相關(guān)答案記錄下來，就形成了以下這些東西。需要說明的是以下答案肯定有很多不完整甚至錯(cuò)誤的地方，需要各位來更正與完善它，千萬不要扔我的雞蛋啊。?
希望本文能夠給即將奔赴筆試考場(chǎng)的同仁些許幫助，更希望更多的人加入到收集整理筆試題與完善答案的這些工作中來，為大家更好的獲得工作機(jī)會(huì)做一點(diǎn)貢獻(xiàn)。?
在此感謝前面兩文的作者的對(duì)筆試題目的收集與整理。?
如有任何意見與建議請(qǐng)通過QQ:6045306,Mail:huijunzi@21cn.com與我聯(lián)系。?
Java基礎(chǔ)方面:?

1、作用域public,private,protected,以及不寫時(shí)的區(qū)別?
答：區(qū)別如下：?
作用域?當(dāng)前類?同一package?子孫類?其他package?
public?√?√?√?√?
protected?√?√?√?×?
friendly?√?√?×?×?
private?√?×?×?×?
不寫時(shí)默認(rèn)為friendly?

2、ArrayList和Vector的區(qū)別,HashMap和Hashtable的區(qū)別?
答：就ArrayList與Vector主要從二方面來說.?
一.同步性:Vector是線程安全的，也就是說是同步的，而ArrayList是線程序不安全的，不是同步的?
二.數(shù)據(jù)增長(zhǎng):當(dāng)需要增長(zhǎng)時(shí),Vector默認(rèn)增長(zhǎng)為原來一培，而ArrayList卻是原來的一半?
就HashMap與HashTable主要從三方面來說。?
一.歷史原因:Hashtable是基于陳舊的Dictionary類的，HashMap是Java?1.2引進(jìn)的Map接口的一個(gè)實(shí)現(xiàn)?
二.同步性:Hashtable是線程安全的，也就是說是同步的，而HashMap是線程序不安全的，不是同步的?
三.值：只有HashMap可以讓你將空值作為一個(gè)表的條目的key或value?

3、char型變量中能不能存貯一個(gè)中文漢字?為什么??
答：是能夠定義成為一個(gè)中文的，因?yàn)閖ava中以u(píng)nicode編碼，一個(gè)char占16個(gè)字節(jié)，所以放一個(gè)中文是沒問題的?

4、多線程有幾種實(shí)現(xiàn)方法,都是什么?同步有幾種實(shí)現(xiàn)方法,都是什么??
答：多線程有兩種實(shí)現(xiàn)方法，分別是繼承Thread類與實(shí)現(xiàn)Runnable接口?
同步的實(shí)現(xiàn)方面有兩種，分別是synchronized,wait與notify?

5、繼承時(shí)候類的執(zhí)行順序問題,一般都是選擇題,問你將會(huì)打印出什么??
答:父類：?
package?test;?
public?class?FatherClass?
{?
public?FatherClass()?
{?
System.out.println("FatherClass?Create");?
}?
}?
子類:?
package?test;?
import?test.FatherClass;?
public?class?ChildClass?extends?FatherClass?
{?
public?ChildClass()?
{?
System.out.println("ChildClass?Create");?
}?
public?static?void?main(String[]?args)?
{?
FatherClass?fc?=?new?FatherClass();?
ChildClass?cc?=?new?ChildClass();?
}?
}?
輸出結(jié)果：?
C:\>java?test.ChildClass?
FatherClass?Create?
FatherClass?Create?
ChildClass?Create?

6、內(nèi)部類的實(shí)現(xiàn)方式??
答：示例代碼如下：?
package?test;?
public?class?OuterClass?
{?
private?class?InterClass?
{?
public?InterClass()?
{?
System.out.println("InterClass?Create");?
}?
}?
public?OuterClass()?
{?
InterClass?ic?=?new?InterClass();?
System.out.println("OuterClass?Create");?
}?
public?static?void?main(String[]?args)?
{?
OuterClass?oc?=?new?OuterClass();?
}?
}?
輸出結(jié)果:?
C:\>java?test/OuterClass?
InterClass?Create?
OuterClass?Create?
再一個(gè)例題：?
public?class?OuterClass?{?
private?double?d1?=?1.0;?
//insert?code?here?
}?
You?need?to?insert?an?inner?class?declaration?at?line?3.?Which?two?inner?class?declarations?are?

valid?(Choose?two.)?
A.?class?InnerOne{?
public?static?double?methoda()?{return?d1;}?
}?
B.?public?class?InnerOne{?
static?double?methoda()?{return?d1;}?
}?
C.?private?class?InnerOne{?
double?methoda()?{return?d1;}?
}?
D.?static?class?InnerOne{?
protected?double?methoda()?{return?d1;}?
}?
E.?abstract?class?InnerOne{?
public?abstract?double?methoda();?
}?
說明如下：?
一.靜態(tài)內(nèi)部類可以有靜態(tài)成員，而非靜態(tài)內(nèi)部類則不能有靜態(tài)成員。?故?A、B?錯(cuò)?
二.靜態(tài)內(nèi)部類的非靜態(tài)成員可以訪問外部類的靜態(tài)變量，而不可訪問外部類的非靜態(tài)變量；return?d1?出錯(cuò)。?

故?D?錯(cuò)?
三.非靜態(tài)內(nèi)部類的非靜態(tài)成員可以訪問外部類的非靜態(tài)變量。?故?C?正確?
四.答案為C、E?

7、垃圾回收機(jī)制,如何優(yōu)化程序??
希望大家補(bǔ)上，謝謝?

8、float型float?f=3.4是否正確??
答:不正確。精度不準(zhǔn)確,應(yīng)該用強(qiáng)制類型轉(zhuǎn)換，如下所示：float?f=(float)3.4?

9、介紹JAVA中的Collection?FrameWork(包括如何寫自己的數(shù)據(jù)結(jié)構(gòu))??
答：Collection?FrameWork如下：?
Collection?
├List?
│├LinkedList?
│├ArrayList?
│└Vector?
│　└Stack?
└Set?
Map?
├Hashtable?
├HashMap?
└WeakHashMap?
Collection是最基本的集合接口，一個(gè)Collection代表一組Object，即Collection的元素（Elements）?
Map提供key到value的映射?

10、Java中異常處理機(jī)制，事件機(jī)制？?

11、JAVA中的多形與繼承？?
希望大家補(bǔ)上，謝謝?

12、抽象類與接口？?
答：抽象類與接口都用于抽象，但是抽象類(JAVA中)可以有自己的部分實(shí)現(xiàn)，而接口則完全是一個(gè)標(biāo)識(shí)(同時(shí)有多重繼承的功能)。?

13、Java?的通信編程，編程題(或問答)，用JAVA?SOCKET編程，讀服務(wù)器幾個(gè)字符，再寫入本地顯示？?
答:Server端程序:?
package?test;?
import?java.net.*;?
import?java.io.*;?

public?class?Server?
{?
private?ServerSocket?ss;?
private?Socket?socket;?
private?BufferedReader?in;?
private?PrintWriter?out;?
public?Server()?
{?
try?
{?
ss=new?ServerSocket(10000);?
while(true)?
{?
socket?=?ss.accept();?
String?RemoteIP?=?socket.getInetAddress().getHostAddress();?
String?RemotePort?=?":"+socket.getLocalPort();?
System.out.println("A?client?come?in!IP:"+RemoteIP+RemotePort);?
in?=?new?BufferedReader(new?

InputStreamReader(socket.getInputStream()));?
String?line?=?in.readLine();?
System.out.println("Cleint?send?is?:"?+?line);?
out?=?new?PrintWriter(socket.getOutputStream(),true);?
out.println("Your?Message?Received!");?
out.close();?
in.close();?
socket.close();?
}?
}catch?(IOException?e)?
{?
out.println("wrong");?
}?
}?
public?static?void?main(String[]?args)?
{?
new?Server();?
}?
};?
Client端程序:?
package?test;?
import?java.io.*;?
import?java.net.*;?

public?class?Client?
{?
Socket?socket;?
BufferedReader?in;?
PrintWriter?out;?
public?Client()?
{?
try?
{?
System.out.println("Try?to?Connect?to?127.0.0.1:10000");?
socket?=?new?Socket("127.0.0.1",10000);?
System.out.println("The?Server?Connected!");?
System.out.println("Please?enter?some?Character:");?
BufferedReader?line?=?new?BufferedReader(new?

InputStreamReader(System.in));?
out?=?new?PrintWriter(socket.getOutputStream(),true);?
out.println(line.readLine());?
in?=?new?BufferedReader(new?InputStreamReader(socket.getInputStream()));?
System.out.println(in.readLine());?
out.close();?
in.close();?
socket.close();?
}catch(IOException?e)?
{?
out.println("Wrong");?
}?
}?
public?static?void?main(String[]?args)?
{?
new?Client();?
}?
};?

14、用JAVA實(shí)現(xiàn)一種排序，JAVA類實(shí)現(xiàn)序列化的方法(二種)？?如在COLLECTION框架中，實(shí)現(xiàn)比較要實(shí)現(xiàn)什么樣的接口？?
答:用插入法進(jìn)行排序代碼如下?
package?test;?
import?java.util.*;?
class?InsertSort?
{?
ArrayList?al;?
public?InsertSort(int?num,int?mod)?
{?
al?=?new?ArrayList(num);?
Random?rand?=?new?Random();?
System.out.println("The?ArrayList?Sort?Before:");?
for?(int?i=0;i<num?;i++?)?
{?
al.add(new?Integer(Math.abs(rand.nextInt())?%?mod?+?1));?
System.out.println("al["+i+"]="+al.get(i));?
}?
}?
public?void?SortIt()?
{?
Integer?tempInt;?
int?MaxSize=1;?
for(int?i=1;i<al.size();i++)?
{?
tempInt?=?(Integer)al.remove(i);?
if(tempInt.intValue()>=((Integer)al.get(MaxSize-1)).intValue())?
{?
al.add(MaxSize,tempInt);?
MaxSize++;?
System.out.println(al.toString());?
}?else?{?
for?(int?j=0;j<MaxSize?;j++?)?
{?
if?

(((Integer)al.get(j)).intValue()>=tempInt.intValue())?
{?
al.add(j,tempInt);?
MaxSize++;?
System.out.println(al.toString());?
break;?
}?
}?
}?
}?
System.out.println("The?ArrayList?Sort?After:");?
for(int?i=0;i<al.size();i++)?
{?
System.out.println("al["+i+"]="+al.get(i));?
}?
}?
public?static?void?main(String[]?args)?
{?
InsertSort?is?=?new?InsertSort(10,100);?
is.SortIt();?
}?
}?
JAVA類實(shí)現(xiàn)序例化的方法是實(shí)現(xiàn)java.io.Serializable接口?
Collection框架中實(shí)現(xiàn)比較要實(shí)現(xiàn)Comparable?接口和?Comparator?接口?

15、編程：編寫一個(gè)截取字符串的函數(shù)，輸入為一個(gè)字符串和字節(jié)數(shù)，輸出為按字節(jié)截取的字符串。?但是要保證漢字不被截半個(gè)，如“我ABC”4，應(yīng)該截為“我AB”，輸入“我ABC漢DEF”，6，應(yīng)該輸出為“我ABC”而不是“我ABC+漢的半個(gè)”。?
答：代碼如下：?
package?test;?

class?SplitString?
{?
String?SplitStr;?
int?SplitByte;?
public?SplitString(String?str,int?bytes)?
{?
SplitStr=str;?
SplitByte=bytes;?
System.out.println("The?String?is:′"+SplitStr+"′SplitBytes="+SplitByte);?
}?
public?void?SplitIt()?
{?
int?loopCount;?

loopCount=(SplitStr.length()%SplitByte==0)?(SplitStr.length()/SplitByte):(SplitStr.length()/Split?

Byte+1);?
System.out.println("Will?Split?into?"+loopCount);?
for?(int?i=1;i<=loopCount?;i++?)?
{?
if?(i==loopCount){?

System.out.println(SplitStr.substring((i-1)*SplitByte,SplitStr.length()));?
}?else?{?

System.out.println(SplitStr.substring((i-1)*SplitByte,(i*SplitByte)));?
}?
}?
}?
public?static?void?main(String[]?args)?
{?
SplitString?ss?=?new?SplitString("test中dd文dsaf中男大3443n中國(guó)43中國(guó)人?

0ewldfls=103",4);?
ss.SplitIt();?
}?
}?

16、JAVA多線程編程。?用JAVA寫一個(gè)多線程程序，如寫四個(gè)線程，二個(gè)加1，二個(gè)對(duì)一個(gè)變量減一，輸出。?
希望大家補(bǔ)上，謝謝?

17、STRING與STRINGBUFFER的區(qū)別。?
答：STRING的長(zhǎng)度是不可變的，STRINGBUFFER的長(zhǎng)度是可變的。如果你對(duì)字符串中的內(nèi)容經(jīng)常進(jìn)行操作，特別是內(nèi)容要修改時(shí)，那么使用StringBuffer，如果最后需要String，那么使用StringBuffer的toString()方法?

Jsp方面?

1、jsp有哪些內(nèi)置對(duì)象?作用分別是什么??
答:JSP共有以下9種基本內(nèi)置組件（可與ASP的6種內(nèi)部組件相對(duì)應(yīng)）：?
　request?用戶端請(qǐng)求，此請(qǐng)求會(huì)包含來自GET/POST請(qǐng)求的參數(shù)?
response?網(wǎng)頁傳回用戶端的回應(yīng)?
pageContext?網(wǎng)頁的屬性是在這里管理?
session?與請(qǐng)求有關(guān)的會(huì)話期?
application?servlet?正在執(zhí)行的內(nèi)容?
out?用來傳送回應(yīng)的輸出?
config?servlet的構(gòu)架部件?
page?JSP網(wǎng)頁本身?
exception?針對(duì)錯(cuò)誤網(wǎng)頁，未捕捉的例外?

2、jsp有哪些動(dòng)作?作用分別是什么??
答:JSP共有以下6種基本動(dòng)作?
jsp:include：在頁面被請(qǐng)求的時(shí)候引入一個(gè)文件。?
jsp:useBean：尋找或者實(shí)例化一個(gè)JavaBean。?
jsp:setProperty：設(shè)置JavaBean的屬性。?
jsp:getProperty：輸出某個(gè)JavaBean的屬性。?
jsp:forward：把請(qǐng)求轉(zhuǎn)到一個(gè)新的頁面。?
jsp:plugin：根據(jù)瀏覽器類型為Java插件生成OBJECT或EMBED標(biāo)記?

3、JSP中動(dòng)態(tài)INCLUDE與靜態(tài)INCLUDE的區(qū)別？?
答：動(dòng)態(tài)INCLUDE用jsp:include動(dòng)作實(shí)現(xiàn)?
<jsp:include?page="included.jsp"?flush="true"?/>它總是會(huì)檢查所含文件中的變化，適合用于包含動(dòng)態(tài)頁面，并且可以帶參數(shù)?
靜態(tài)INCLUDE用include偽碼實(shí)現(xiàn),定不會(huì)檢查所含文件的變化，適用于包含靜態(tài)頁面?
<%@?include?file="included.htm"?%>?

4、兩種跳轉(zhuǎn)方式分別是什么?有什么區(qū)別??
答：有兩種，分別為：?
<jsp:include?page="included.jsp"?flush="true">?
<jsp:forward?page=?"nextpage.jsp"/>?
前者頁面不會(huì)轉(zhuǎn)向include所指的頁面，只是顯示該頁的結(jié)果，主頁面還是原來的頁面。執(zhí)行完后還會(huì)回來，相當(dāng)于函數(shù)調(diào)用。并且可以帶參數(shù).后者完全轉(zhuǎn)向新頁面，不會(huì)再回來。相當(dāng)于go?to?語句。?

Servlet方面?

1、說一說Servlet的生命周期??
答:servlet有良好的生存期的定義，包括加載和實(shí)例化、初始化、處理請(qǐng)求以及服務(wù)結(jié)束。這個(gè)生存期由javax.servlet.Servlet接口的init,service和destroy方法表達(dá)。?

2、Servlet版本間(忘了問的是哪兩個(gè)版本了)的不同??
希望大家補(bǔ)上，謝謝?

3、JAVA?SERVLET?API中forward()?與redirect()的區(qū)別？?
答:前者僅是容器中控制權(quán)的轉(zhuǎn)向，在客戶端瀏覽器地址欄中不會(huì)顯示出轉(zhuǎn)向后的地址；后者則是完全的跳轉(zhuǎn)，瀏覽器將會(huì)得到跳轉(zhuǎn)的地址，并重新發(fā)送請(qǐng)求鏈接。這樣，從瀏覽器的地址欄中可以看到跳轉(zhuǎn)后的鏈接地址。所以，前者更加高效，在前者可以滿足需要時(shí)，盡量使用forward()方法，并且，這樣也有助于隱藏實(shí)際的鏈接。在有些情況下，比如，需要跳轉(zhuǎn)到一個(gè)其它服務(wù)器上的資源，則必須使用sendRedirect()方法。?

4、Servlet的基本架構(gòu)?
public?class?ServletName?extends?HttpServlet?{?
public?void?doPost(HttpServletRequest?request,?HttpServletResponse?response)?throws?
ServletException,?IOException?{?
}?
public?void?doGet(HttpServletRequest?request,?HttpServletResponse?response)?throws?
ServletException,?IOException?{?
}?
}?

Jdbc、Jdo方面?

1、可能會(huì)讓你寫一段Jdbc連Oracle的程序,并實(shí)現(xiàn)數(shù)據(jù)查詢.?
答:程序如下：?
package?hello.ant;?
import?java.sql.*;?
public?class?jdbc?
{?
String?dbUrl="jdbc:oracle:thin:@127.0.0.1:1521:orcl"?
String?theUser="admin"?
String?thePw="manager"?
Connection?c=null;?
Statement?conn;?
ResultSet?rs=null;?
public?jdbc()?
{?
try{?
Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();?
c?=?DriverManager.getConnection(dbUrl,theUser,thePw);?
conn=c.createStatement();?
}catch(Exception?e){?
e.printStackTrace();?
}?
}?
public?boolean?executeUpdate(String?sql)?
{?
try?
{?
conn.executeUpdate(sql);?
return?true;?
}?
catch?(SQLException?e)?
{?
e.printStackTrace();?
return?false;?
}?
}?
public?ResultSet?executeQuery(String?sql)?
{?
rs=null;?
try?
{?
rs=conn.executeQuery(sql);?
}?
catch?(SQLException?e)?
{?
e.printStackTrace();?
}?
return?rs;?
}?
public?void?close()?
{?
try?
{?
conn.close();?
c.close();?
}?
catch?(Exception?e)?
{?
e.printStackTrace();?
}?
}?
public?static?void?main(String[]?args)?
{?
ResultSet?rs;?
jdbc?conn?=?new?jdbc();?
rs=conn.executeQuery("select?*?from?test");?
try{?
while?(rs.next())?
{?
System.out.println(rs.getString("id"));?
System.out.println(rs.getString("name"));?
}?
}catch(Exception?e)?
{?
e.printStackTrace();?
}?
}?
}?

2、Class.forName的作用?為什么要用??
答：調(diào)用該訪問返回一個(gè)以字符串指定類名的類的對(duì)象。?

3、Jdo是什么??
答:JDO是Java對(duì)象持久化的新的規(guī)范，為java?data?object的簡(jiǎn)稱,也是一個(gè)用于存取某種數(shù)據(jù)倉(cāng)庫中的對(duì)象的標(biāo)準(zhǔn)化API。JDO提供了透明的對(duì)象存儲(chǔ)，因此對(duì)開發(fā)人員來說，存儲(chǔ)數(shù)據(jù)對(duì)象完全不需要額外的代碼（如JDBC?API的使用）。這些繁瑣的例行工作已經(jīng)轉(zhuǎn)移到JDO產(chǎn)品提供商身上，使開發(fā)人員解脫出來，從而集中時(shí)間和精力在業(yè)務(wù)邏輯上。另外，JDO很靈活，因?yàn)樗梢栽谌魏螖?shù)據(jù)底層上運(yùn)行。JDBC只是面向關(guān)系數(shù)據(jù)庫（RDBMS)JDO更通用，提供到任何數(shù)據(jù)底層的存儲(chǔ)功能，比如關(guān)系數(shù)據(jù)庫、文件、XML以及對(duì)象數(shù)據(jù)庫（ODBMS）等等，使得應(yīng)用可移植性更強(qiáng)。?

4、在ORACLE大數(shù)據(jù)量下的分頁解決方法。一般用截取ID方法，還有是三層嵌套方法。?
答:一種分頁方法?
<%?
int?i=1;?
int?numPages=14;?
String?pages?=?request.getParameter("page")?;?
int?currentPage?=?1;?
currentPage=(pages==null)?(1):{Integer.parseInt(pages)}?
sql?=?"select?count(*)?from?tables"?
ResultSet?rs?=?DBLink.executeQuery(sql)?;?
while(rs.next())?i?=?rs.getInt(1)?;?
int?intPageCount=1;?
intPageCount=(i%numPages==0)?(i/numPages):(i/numPages+1);?
int?nextPage?;?
int?upPage;?
nextPage?=?currentPage+1;?
if?(nextPage>=intPageCount)?nextPage=intPageCount;?
upPage?=?currentPage-1;?
if?(upPage<=1)?upPage=1;?
rs.close();?
sql="select?*?from?tables"?
rs=DBLink.executeQuery(sql);?
i=0;?
while((i<numPages*(currentPage-1))&&rs.next()){i++;}?
%>?
//輸出內(nèi)容?
//輸出翻頁連接?
合計(jì):<%=currentPage%>/<%=intPageCount%><a?href="List.jsp?page=1"?temp_href="List.jsp?page=1">第一頁</a><a?

href="List.jsp?page=<%=upPage%>"?temp_href="List.jsp?page=<%=upPage%>">上一頁</a>?
<%?
for(int?j=1;j<=intPageCount;j++){?
if(currentPage!=j){?
%>?
<a?href="list.jsp?page=<%=j%>"?temp_href="list.jsp?page=<%=j%>">[<%=j%>]</a>?
<%?
}else{?
out.println(j);?
}?
}?
%>?
<a?href="List.jsp?page=<%=nextPage%&gt;"?temp_href="List.jsp?page=<%=nextPage%>">下一頁</a><a?href="List.jsp?page=<%=intPageCount%&gt;"?temp_href="List.jsp?page=<%=intPageCount%>">最后頁?

</a>?

Xml方面?

1、xml有哪些解析技術(shù)?區(qū)別是什么??
答:有DOM,SAX,STAX等?
DOM:處理大型文件時(shí)其性能下降的非常厲害。這個(gè)問題是由DOM的樹結(jié)構(gòu)所造成的，這種結(jié)構(gòu)占用的內(nèi)存較多，而且DOM必須在解析文件之前把整個(gè)文檔裝入內(nèi)存,適合對(duì)XML的隨機(jī)訪問SAX:不現(xiàn)于DOM,SAX是事件驅(qū)動(dòng)型的XML解析方式。它順序讀取XML文件，不需要一次全部裝載整個(gè)文件。當(dāng)遇到像文件開頭，文檔結(jié)束，或者標(biāo)簽開頭與標(biāo)簽結(jié)束時(shí)，它會(huì)觸發(fā)一個(gè)事件，用戶通過在其回調(diào)事件中寫入處理代碼來處理XML文件，適合對(duì)XML的順序訪問?
STAX:Streaming?API?for?XML?(StAX)?

2、你在項(xiàng)目中用到了xml技術(shù)的哪些方面?如何實(shí)現(xiàn)的??
答:用到了數(shù)據(jù)存貯，信息配置兩方面。在做數(shù)據(jù)交換平臺(tái)時(shí)，將不能數(shù)據(jù)源的數(shù)據(jù)組裝成XML文件，然后將XML文件壓縮打包加密后通過網(wǎng)絡(luò)傳送給接收者，接收解密與解壓縮后再同XML文件中還原相關(guān)信息進(jìn)行處理。在做軟件配置時(shí)，利用XML可以很方便的進(jìn)行，軟件的各種配置參數(shù)都存貯在XML文件中。?

3、用jdom解析xml文件時(shí)如何解決中文問題?如何解析??
答:看如下代碼,用編碼方式加以解決?
package?test;?
import?java.io.*;?
public?class?DOMTest?
{?
private?String?inFile?=?"c:\\people.xml"?
private?String?outFile?=?"c:\\people.xml"?
public?static?void?main(String?args[])?
{?
new?DOMTest();?
}?
public?DOMTest()?
{?
try?
{?
javax.xml.parsers.DocumentBuilder?builder?=?

javax.xml.parsers.DocumentBuilderFactory.newInstance().newDocumentBuilder();?
org.w3c.dom.Document?doc?=?builder.newDocument();?
org.w3c.dom.Element?root?=?doc.createElement("老師");?
org.w3c.dom.Element?wang?=?doc.createElement("王");?
org.w3c.dom.Element?liu?=?doc.createElement("劉");?
wang.appendChild(doc.createTextNode("我是王老師"));?
root.appendChild(wang);?
doc.appendChild(root);?
javax.xml.transform.Transformer?transformer?=?
javax.xml.transform.TransformerFactory.newInstance().newTransformer();?
transformer.setOutputProperty(javax.xml.transform.OutputKeys.ENCODING,?"gb2312");?
transformer.setOutputProperty(javax.xml.transform.OutputKeys.INDENT,?"yes");?

transformer.transform(new?javax.xml.transform.dom.DOMSource(doc),?
new?

javax.xml.transform.stream.StreamResult(outFile));?
}?
catch?(Exception?e)?
{?
System.out.println?(e.getMessage());?
}?
}?
}?

4、編程用JAVA解析XML的方式.?
答:用SAX方式解析XML，XML文件如下：?
<?xml?version="1.0"?encoding="gb2312"?>?
<person>?
<name>王小明</name>?
<college>信息學(xué)院</college>?
<telephone>6258113</telephone>?
<notes>男,1955年生,博士，95年調(diào)入海南大學(xué)</notes>?
</person>?
事件回調(diào)類SAXHandler.java?
import?java.io.*;?
import?java.util.Hashtable;?
import?org.xml.sax.*;?
public?class?SAXHandler?extends?HandlerBase?
{?
private?Hashtable?table?=?new?Hashtable();?
private?String?currentElement?=?null;?
private?String?currentValue?=?null;?
public?void?setTable(Hashtable?table)?
{?
this.table?=?table;?
}?
public?Hashtable?getTable()?
{?
return?table;?
}?
public?void?startElement(String?tag,?AttributeList?attrs)?
throws?SAXException?
{?
currentElement?=?tag;?
}?
public?void?characters(char[]?ch,?int?start,?int?length)?
throws?SAXException?
{?
currentValue?=?new?String(ch,?start,?length);?
}?
public?void?endElement(String?name)?throws?SAXException?
{?
if?(currentElement.equals(name))?
table.put(currentElement,?currentValue);?
}?
}?
JSP內(nèi)容顯示源碼,SaxXml.jsp:?
<HTML>?
<HEAD>?
<TITLE>剖析XML文件people.xml</TITLE>?
</HEAD>?
<BODY>?
<%@?page?errorPage="ErrPage.jsp"?
contentType="text/html;charset=GB2312"?%>?
<%@?page?import="java.io.*"?%>?
<%@?page?import="java.util.Hashtable"?%>?
<%@?page?import="org.w3c.dom.*"?%>?
<%@?page?import="org.xml.sax.*"?%>?
<%@?page?import="javax.xml.parsers.SAXParserFactory"?%>?
<%@?page?import="javax.xml.parsers.SAXParser"?%>?
<%@?page?import="SAXHandler"?%>?
<%?
File?file?=?new?File("c:\\people.xml");?
FileReader?reader?=?new?FileReader(file);?
Parser?parser;?
SAXParserFactory?spf?=?SAXParserFactory.newInstance();?
SAXParser?sp?=?spf.newSAXParser();?
SAXHandler?handler?=?new?SAXHandler();?
sp.parse(new?InputSource(reader),?handler);?
Hashtable?hashTable?=?handler.getTable();?
out.println("<TABLE?BORDER=2><CAPTION>教師信息表</CAPTION>");?
out.println("<TR><TD>姓名</TD>"?+?"<TD>"?+?
(String)hashTable.get(new?String("name"))?+?"</TD></TR>");?
out.println("<TR><TD>學(xué)院</TD>"?+?"<TD>"?+?
(String)hashTable.get(new?String("college"))+"</TD></TR>");?
out.println("<TR><TD>電話</TD>"?+?"<TD>"?+?
(String)hashTable.get(new?String("telephone"))?+?"</TD></TR>");?
out.println("<TR><TD>備注</TD>"?+?"<TD>"?+?
(String)hashTable.get(new?String("notes"))?+?"</TD></TR>");?
out.println("</TABLE>");?
%>?
</BODY>?
</HTML>?

EJB方面?

1、EJB2.0有哪些內(nèi)容?分別用在什么場(chǎng)合??EJB2.0和EJB1.1的區(qū)別??
答：規(guī)范內(nèi)容包括Bean提供者，應(yīng)用程序裝配者，EJB容器，EJB配置工具，EJB服務(wù)提供者，系統(tǒng)管理員。這里面，EJB容器是EJB之所以能夠運(yùn)行的核心。EJB容器管理著EJB的創(chuàng)建，撤消，激活，去活，與數(shù)據(jù)庫的連接等等重要的核心工作。JSP,Servlet,EJB,JNDI,JDBC,JMS.....?

2、EJB與JAVA?BEAN的區(qū)別？?
答:Java?Bean?是可復(fù)用的組件，對(duì)Java?Bean并沒有嚴(yán)格的規(guī)范，理論上講，任何一個(gè)Java類都可以是一個(gè)Bean。但通常情況下，由于Java?Bean是被容器所創(chuàng)建（如Tomcat)的，所以Java?Bean應(yīng)具有一個(gè)無參的構(gòu)造器，另外，通常Java?Bean還要實(shí)現(xiàn)Serializable接口用于實(shí)現(xiàn)Bean的持久性。Java?Bean實(shí)際上相當(dāng)于微軟COM模型中的本地進(jìn)程內(nèi)COM組件，它是不能被跨進(jìn)程訪問的。Enterprise?Java?Bean?相當(dāng)于DCOM，即分布式組件。它是基于Java的遠(yuǎn)程方法調(diào)用（RMI）技術(shù)的，所以EJB可以被遠(yuǎn)程訪問（跨進(jìn)程、跨計(jì)算機(jī)）。但EJB必須被布署在諸如Webspere、WebLogic這樣的容器中，EJB客戶從不直接訪問真正的EJB組件，而是通過其容器訪問。EJB容器是EJB組件的代理，EJB組件由容器所創(chuàng)建和管理。客戶通過容器來訪問真正的EJB組件。?

3、EJB的基本架構(gòu)?
答:一個(gè)EJB包括三個(gè)部分:?
Remote?Interface?接口的代碼?
package?Beans;?
import?javax.ejb.EJBObject;?
import?java.rmi.RemoteException;?
public?interface?Add?extends?EJBObject?
{?
//some?method?declare?
}?
Home?Interface?接口的代碼?
package?Beans;?
import?java.rmi.RemoteException;?
import?jaax.ejb.CreateException;?
import?javax.ejb.EJBHome;?
public?interface?AddHome?extends?EJBHome?
{?
//some?method?declare?
}?
EJB類的代碼?
package?Beans;?
import?java.rmi.RemoteException;?
import?javax.ejb.SessionBean;?
import?javx.ejb.SessionContext;?
public?class?AddBean?Implements?SessionBean?
{?
//some?method?declare?
}?

J2EE,MVC方面?

1、MVC的各個(gè)部分都有那些技術(shù)來實(shí)現(xiàn)?如何實(shí)現(xiàn)??
答:MVC是Model－View－Controller的簡(jiǎn)寫。"Model"?代表的是應(yīng)用的業(yè)務(wù)邏輯（通過JavaBean，EJB組件實(shí)現(xiàn)），?"View"?是應(yīng)用的表示面（由JSP頁面產(chǎn)生），"Controller"?是提供應(yīng)用的處理過程控制（一般是一個(gè)Servlet），通過這種設(shè)計(jì)模型把應(yīng)用邏輯，處理過程和顯示邏輯分成不同的組件實(shí)現(xiàn)。這些組件可以進(jìn)行交互和重用。?

2、應(yīng)用服務(wù)器與WEB?SERVER的區(qū)別？?
希望大家補(bǔ)上，謝謝?

3、J2EE是什么？?
答:Je22是Sun公司提出的多層(multi-diered),分布式(distributed),基于組件(component-base)的企業(yè)級(jí)應(yīng)用模型(enterpriese?application?model).在這樣的一個(gè)應(yīng)用系統(tǒng)中，可按照功能劃分為不同的組件，這些組件又可在不同計(jì)算機(jī)上，并且處于相應(yīng)的層次(tier)中。所屬層次包括客戶層(clietn?tier)組件,web層和組件,Business層和組件,企業(yè)信息系統(tǒng)(EIS)層。?

4、WEB?SERVICE名詞解釋。JSWDL開發(fā)包的介紹。JAXP、JAXM的解釋。SOAP、UDDI,WSDL解釋。?
答：Web?Service描述語言WSDL?
SOAP即簡(jiǎn)單對(duì)象訪問協(xié)議(Simple?Object?Access?Protocol)，它是用于交換XML編碼信息的輕量級(jí)協(xié)議。?
UDDI?的目的是為電子商務(wù)建立標(biāo)準(zhǔn)；UDDI是一套基于Web的、分布式的、為Web?Service提供的、信息注冊(cè)中心的實(shí)現(xiàn)標(biāo)準(zhǔn)規(guī)范，同時(shí)也包含一組使企業(yè)能將自身提供的Web?Service注冊(cè)，以使別的企業(yè)能夠發(fā)現(xiàn)的訪問協(xié)議的實(shí)現(xiàn)標(biāo)準(zhǔn)。?

5、BS與CS的聯(lián)系與區(qū)別。?
希望大家補(bǔ)上，謝謝?

6、STRUTS的應(yīng)用(如STRUTS架構(gòu))?
答：Struts是采用Java?Servlet/JavaServer?Pages技術(shù)，開發(fā)Web應(yīng)用程序的開放源碼的framework。?采用Struts能開發(fā)出基于MVC(Model-View-Controller)設(shè)計(jì)模式的應(yīng)用構(gòu)架。?Struts有如下的主要功能：?
一.包含一個(gè)controller?servlet，能將用戶的請(qǐng)求發(fā)送到相應(yīng)的Action對(duì)象。?
二.JSP自由tag庫，并且在controller?servlet中提供關(guān)聯(lián)支持，幫助開發(fā)員創(chuàng)建交互式表單應(yīng)用。?
三.提供了一系列實(shí)用對(duì)象：XML處理、通過Java?reflection?APIs自動(dòng)處理JavaBeans屬性、國(guó)際化的提示和消息。?

設(shè)計(jì)模式方面?

1、開發(fā)中都用到了那些設(shè)計(jì)模式?用在什么場(chǎng)合??
答：每個(gè)模式都描述了一個(gè)在我們的環(huán)境中不斷出現(xiàn)的問題，然后描述了該問題的解決方案的核心。通過這種方式，你可以無數(shù)次地使用那些已有的解決方案，無需在重復(fù)相同的工作。主要用到了MVC的設(shè)計(jì)模式。用來開發(fā)JSP/Servlet或者J2EE的相關(guān)應(yīng)用。簡(jiǎn)單工廠模式等。?

2、UML方面?
答：標(biāo)準(zhǔn)建模語言UML。用例圖,靜態(tài)圖(包括類圖、對(duì)象圖和包圖),行為圖,交互圖(順序圖,合作圖),實(shí)現(xiàn)圖,?

JavaScript方面?

1、如何校驗(yàn)數(shù)字型??
var?re=/^\d{1,8}$|\.\d{1,2}$/;?
var?str=document.form1.all(i).value;?
var?r=str.match(re);?
if?(r==null)?
{?
sign=-4;?
break;?
}?
else{?
document.form1.all(i).value=parseFloat(str);?
}?

CORBA方面?

1、CORBA是什么?用途是什么??
答：CORBA?標(biāo)準(zhǔn)是公共對(duì)象請(qǐng)求代理結(jié)構(gòu)(Common?Object?Request?Broker?Architecture)，由對(duì)象管理組織?(Object?Management?Group，縮寫為?OMG)標(biāo)準(zhǔn)化。它的組成是接口定義語言(IDL),?語言綁定(binding:也譯為聯(lián)編)和允許應(yīng)用程序間互操作的協(xié)議。?其目的為：?
用不同的程序設(shè)計(jì)語言書寫?
在不同的進(jìn)程中運(yùn)行?
為不同的操作系統(tǒng)開發(fā)?

LINUX方面?

1、LINUX下線程，GDI類的解釋。?
答：LINUX實(shí)現(xiàn)的就是基于核心輕量級(jí)進(jìn)程的"一對(duì)一"線程模型，一個(gè)線程實(shí)體對(duì)應(yīng)一個(gè)核心輕量級(jí)進(jìn)程，而線程之間的管理在核外函數(shù)庫中實(shí)現(xiàn)。?
GDI類為圖像設(shè)備編程接口類庫。

Hibernate:?簡(jiǎn)述?Hibernate?和?JDBC?的優(yōu)缺點(diǎn)??如何書寫一個(gè)?one?to?many?配置文件.

Spring?的依賴注入是什么意思??給一個(gè)?Bean?的?message?屬性,?字符串類型,?注入值為?"Hello"?的?XML?配置文件該怎么寫?

SCJP?模擬題200道附答案

Q1?Which?of?the?following?statements?are?valid,?given?the?following?variable?declarations:?boolean?a;?boolean?b;?int?c;?
1)?(a?|?b)?
2)(a?||?a)?
3)(a?^?b)?|?c?
4)(a?&?c)?
5)(a?&&?c)?

Q2?Which?of?the?following?can?be?applied?to?constructors:?
1)?final?
2)?static?
3)?synchronized?
4)?native?
5)?None?of?these.?

Q3?Which?of?the?following?retain?their?preferred?size?(width?and?height)?when?added?(individually)?to?the?North?section?of?a?container?with?a?BorderLayout?(assume?that?no?other?components?or?containers?are?present?in?the?North?section).?
1)?TextArea?
2)?Button?
3)?TextField?
4)?Checkbox?
5)?None.?All?of?these?mentioned?components?will?only?retain?their?preferred?height.?

Q4?Which?of?the?following?are?legal?names?for?variables.?
1)?_int?
2)?%large?
3)?$fred?
4)?Integer?
5)?2much?

Q5?Which?of?the?following?are?correct?ways?to?create?a?font.?
1)?Font?f?=?new?Font("Serif",?Font.BOLD,?24);?
2)?Font?f?=?new?Font(Font.SERIF,?"Bold",?24);?
3)?Font?f?=?new?Font("Serif",?"Bold",?24);?
4)?Font?f?=?new?Font(Font.SERIF,?Font.BOLD,?24);?

Q6?Select?the?correct?statements?regarding?the?following?piece?of?code.?
File?f?=?new?File("c:\\large.txt");?
1)?On?execution,?a?file?called?"large.txt"?will?be?created?on?the?local?harddisk.?
2)?The?code?fails?to?compile?on?a?UNIX?machine,?because?the?directory?separator?is?not?correct.?
3)?A?file?is?NOT?created?on?the?harddisk?when?this?code?is?executed.?
4)?An?exception?is?thrown?at?runtime?if?the?file?"large.txt"?already?exists.?
5)?The?code?fails?to?compile,?since?this?is?not?a?valid?constructor?for?the?File?class.?

Q7?Which?of?the?following?statements?are?correct?regarding?the?RandomAccessFile?class??
1)?An?IOException?is?thrown?if?the?specified?file?doesn't?exist?when?created?using?the?"r"?mode.?
2)?This?class?has?a?method?which?allows?a?file?to?be?deleted?from?the?harddisk.?
3)?It?is?possible?to?use?this?class?in?conjunction?with?the?DataInputStream?class.?
4)?When?used?with?the?"rw"?mode,?the?specified?file?is?created?on?a?diskdrive,?if?it?doesn't?already?exist.?
5)?There?are?methods?to?read?and?write?primatives?(eg,?readInt(),?writeInt(),?etc).?

Q8?Consider?the?following?piece?of?code?and?select?the?correct?statement?from?the?following.?
1.String?s?=?new?String("abcdefgh");?
2.s.replace('d',?'q');?
3.System.out.println(s);?

1)?The?code?fails?to?compile,?reporting?an?error?at?line?2.?Strings?are?immutable,?and?therefore?a?replace()?method?is?meaningless.?
2)?The?code?compiles?correctly,?and?displays?the?text?"abcqefgh".?
3)?The?code?compiles?correctly,?and?displays?the?text?"abcdefgh".?
4)?The?code?compiles,?but?an?exception?is?thrown?when?line?2?is?executed.?
5)?The?code?compiles,?but?an?exception?is?thrown?at?line?3.?

Q9?Which?of?the?following?keywords?can?be?applied?to?the?variables?or?methods?of?an?interface.?
1)?static?
2)?private?
3)?synchronised?
4)?protected?
5)?public?

Q10?True?or?False.?
Only?Frames?can?contain?menu?bars?or?pull-down?menus.?
1)?True?
2)?False.?

Q11?Consider?the?following?piece?of?code?and?select?the?correct?statement(s):?
1.?class?A{?
2.?protected?int?method(){?
3.?}?
4.?}?
5.?
6.?class?B?extends?A{?
7.?int?method(){?
8.?}?
9.?}?
1)?The?code?fails?to?compile,?because?you?can't?override?a?method?to?be?more?private?than?its?parent.?
2)?The?code?fails?to?compile,?because?method()?is?declared?as?protected,?and?is?therefore?not?available?to?any?subclass.?
3)?The?code?compiles?correctly,?but?throws?a?NullPointerException?at?runtime.?
4)?The?code?fails?to?compile.?However,?it?can?be?made?to?compile?correctly?by?prefixing?line?7?with?the?access?qualifier?"public".?
5)?The?code?fails?to?compile.?However,?it?can?be?made?to?compile?correctly?by?prefixing?line?7?with?the?access?qualifier?"protected".?

Q12?True?or?False.?

The?Throwable?class?is?the?superclass?of?all?exceptions?in?the?Java?language.?
1)?True?
2)?False?

Q13?Consider?the?following?piece?of?code?(assume?the?Graphics?context?g?is?defined?correctly):?
g.setBackground(Color.red);?
g.setForeground(Color.white);?
g.drawLine(10,?10,?50,?10);?
g.setForeground(Color.blue);?
g.drawRect(100,?100,?50,?50);?

What?is?displayed?when?this?code?is?executed.?
1)?A?blue?line?from?(10,10)?to?(50,10)?and?a?blue?rectangle?with?upper?left?corner?at?(100,100).?
2)?A?white?line?from?(10,10)?to?(50,10)?and?a?blue?square?with?top?left?corner?at?(100,100).?
3)?A?white?line?from?(10,10)?to?(10,50)?and?a?blue?square?with?lower?left?corner?at?(100,100).?
4)?A?red?line?from?(10,?10)?to?(50,10)?and?a?red?square?with?upper?left?corner?at?(100,100).?
5)?Nothing?is?displayed.?You?must?first?issue?a?repaint()?command.?

Q14?Consider?the?following?piece?of?code.?
class?Test{?
public?static?void?main(String?[]?args){?
System.out.println(args[3]);?
}?
}?
When?the?following?is?typed?at?the?command?line,?what?is?displayed:?
java?Test?Metallica?Justice?For?All?
1)?All?
2)?For?
3)?Justice?
4)?Nothing.?
5)?Nothing.?An?ArrayIndexOutOfBoundsException?is?thrown?

Q15?Consider?the?following?piece?of?code.?
1.?String?s?=?"abcd";?
2.?Integer?x?=?new?Integer(3);?
3.?String?s2?=?s?+?4;?
4.?s2?=?null;?
5.?s?=?null;?

Following?the?execution?of?which?line?above,?is?the?object?referenced?by?s2?available?for?garbage?collection.?
1)?Line?5?
2)?It?is?not?possible?to?say?when?an?object?is?available?for?garbage?collection.?
3)?Line?4?
4)?The?objects?are?not?available?until?the?executing?thread?is?ended.?

Q16?What?is?displayed?when?the?following?piece?of?code?is?compiled?and?executed:?
class?Test{?
public?static?void?main(String?[]?args){?
Base?b?=?new?Subclass();?
System.out.println(b.x);?
System.out.println(b.method());?
}?
}?

class?Base{?
int?x?=?2;?
int?method(){?
return?x;?
}?
}?

class?Subclass?extends?Base{?
int?x?=?3;?
int?method(){?
return?x;?
}?
}?

1)?Nothing.?The?code?fails?to?compile?because?the?object?b?is?not?created?in?a?valid?way.?
2)?2?
3?
3)?2?
2?
4)?3?
3?
5)?3?
2?

Q17?What?is?displayed?when?the?following?is?executed:?
String?s1?=?"aaa";?
s1.concat("bbb");?
System.out.println(s1);?
1)?The?string?"aaa".?
2)?The?string?"aaabbb".?
3)?Nothing.?concat()?is?not?a?valid?method?in?the?String?class.?
4)?The?string?"bbbaaa".?
5)?The?string?"bbb".?

Q18?True?or?False.?
The?following?is?a?valid?way?to?construct?a?StringBuffer.?
StringBuffer?sb1?=?"abcd";?
1)?True?
2)?False?

Q19?What?is?the?output?of?the?following?piece?of?code:?
1.?int?x?=?6;?
2.?double?d?=?7.7;?
3.?
4.?System.out.println((x?>?d)???99.9?:?9);?

1)?9?
2)?9.0?
3)?99.9?
4)?Nothing.?An?ArithmeticException?is?thrown?at?line?4.?
5)?6?

Q20?Which?of?the?following?can?be?put?in?applet?tags??(select?all?the?correct?answers)?
1)?CODE?
2)?WIDTH?
3)?HEIGHT?
4)?PARAM?
5)?ARCHIVE?

Q21?What?is?printed?out?following?the?execution?of?the?code?below:?
1.?class?Test{?
2.?static?String?s;?
3.?public?static?void?main(String?[]args){?
4.?int?x?=?4;?
5.?if?(x?<?4)?
6.?System.out.println("Val?=?"?+?x);?
7.?else?
8.?System.out.println(s);?
9.?}?
10.?}?
Nothing.?The?code?fails?to?compile?because?the?String?s?isn't?declared?correctly.?
1)?The?text?"Val?=?null"?is?displayed.?
2)?The?string?"Val?=?"?is?displayed.?
3)?The?text?"null"?is?displayed.?
4)?A?blank?line?of?text?is?printed.?

Q22?True?or?False.?
The?StringBuffer?class?does?not?have?a?concat()?method.?
1)?True?
2)?False?

Q23?What?is?displayed?when?the?following?piece?of?code?is?executed?(assume?the?graphics?context,?g,?is?correctly?set?up):?
g.drawString("abc",?10,?10);?
1)?The?text?"abc"?with?the?lower?left?part?of?"a"?located?at?x?=?10,?y?=?10.?
2)?The?text?"abc"?with?the?upper?left?part?of?"a"?located?at?x?=?10,?y?=?10.?
3)?Nothing.?This?is?not?a?valid?method.?

Q24?True?or?False.?
Anonymous?classes?cannot?have?constructors.?
1)?True?
2)?False?

Q25?To?reference?a?JAR?from?a?web?page,?which?of?the?following?keywords?are?used:?
1)?jar?
2)?class?
3)?zip?
4)?archive?
5)?package?

Q26?

Analyse?the?following?2?classes?and?select?the?correct?statements.?
class?A{?
private?int?x?=?0;?
static?int?y?=?1;?
protected?int?q?=?2;?
}?

class?B?extends?A{?
void?method(){?
System.out.println(x);?
System.out.println(y);?
System.out.println(q);?
}?
}?

1)?The?code?fails?to?compile?because?the?variable?x?is?not?available?to?class?B.?
2)?The?code?compiles?correctly,?and?the?following?is?displayed:?0?1?2?
3)?The?code?fails?to?compile?because?you?can't?subclass?a?class?with?private?variables.?
4)?Removing?the?line?"System.out.println(x)"?will?allow?the?code?to?compile?correctly.?
5)?The?compiler?will?complain?that?the?variable?x?in?class?B?is?undefined.?

Q27?Which?of?the?following?interfaces?can?be?used?to?manage?a?collection?of?elements,?with?no?duplication.?
1)?List?
2)?Vector?
3)?Set?

Q28?Which?of?the?following?statements?are?true?regarding?inner?classes.?
1)?Variables?defined?inside?inner?classes?cannot?be?static.?
2)?Variables?defined?inside?inner?classes?cannot?be?static?unless?the?inner?class?itself?is?static.?
3)?Non-static?inner?classes?(which?are?not?defined?in?a?method)?have?access?to?all?class?and?instance?variables,?regardless?of?the?access?qualifier?of?those?variables.?
4)?An?inner?class?can?actually?be?a?subclass?of?the?outer?class?
5)?Inner?classes?can?be?declared?as?private.?Top?level,?outer?classes?cannot.?

Q29?Which?of?the?following?are?valid?ways?to?define?an?abstract?method.?
1)?abstract?void?Test();?
2)?abstract?void?Test()?{}?
3)?static?abstract?void?Test();?
4)?final?abstract?void?Test();?
5)?Methods?cannot?be?defined?as?abstract,?only?variables?can?be?abstract.?

Q30?Consider?the?following:?
class?A?extends?Integer{?
int?x?=?0;?
}?
Select?all?valid?statements.?
1)?The?code?will?compile?correctly.?
2)?The?code?will?not?compile?because?Integer?is?final?and?cannot?be?subclassed.?
3)?The?code?will?not?compile?because?class?A?has?no?methods?or?constructor.?
4)?The?code?will?compile?correctly,?but?will?throw?an?ArithmeticException?at?runtime.?

Q31?Consider?the?following?and?select?the?correct?statement(s):?
interface?A{?
int?x?=?0;?
A(){?
x=?5;?
}?
A(int?s){?
x?=?s;?
}?
}?
1)?This?is?a?valid?piece?of?code?and?it?compiles?correctly.?
2)?The?default?constructor?is?not?required?since?the?compiler?will?create?one?for?you.?
3)?The?code?fails?to?compile?because?interfaces?cannot?have?more?than?1?constructor.?
4)?The?code?fails?to?compile?because?an?interface?cannot?have?any?constructors.?
5)?The?code?fails?to?compile,?because?a?class?must?have?more?than?1?character?in?it's?name.?

Q32?True?or?False.?
A?try?block?always?needs?a?catch?or?a?finally?block?(either?or?both,?but?not?none).?
1)?True?
2)?False

Q33?Which?of?the?following?are?valid?ways?to?declare?the?main()?method?which?is?used?to?start?a?Java?program.?
1)?public?static?void?main(String?[]?args)?
2)?static?public?void?main(String?[]?args)?
3)?public?void?main(String?args?[])?
4)?public?static?void?main(String?args[])?
5)?public?static?void?main(String?args)?

Q34?Consider?the?following?piece?of?code:?
boolean?b?=?true;?
System.out.println(b);?
What?is?displayed?when?this?code?is?executed??
1)?The?text?"true"?is?displayed.?
2)?The?text?"1"?is?displayed?
3)?The?code?fails?to?compile,?because?conversion?string?conversion?in?ths?System.out.println()?method?only?applies?to?integers.?
4)?The?code?compiles?but?nothing?is?displayed?upon?execution.?
5)?The?code?fails?to?compile.?However,?changing?the?first?line?to?"boolean?b?=?TRUE;"?will?correctly?declare?a?boolean,?and?the?code?will?compile?and?display?"TRUE".?

Q35?Which?of?the?following?pieces?of?code?compiles?without?any?errors??
1)?StringBuffer?sb1?=?"abcd";?
2)?Boolean?b?=?new?Boolean("abcd");?
3)?byte?b?=?255;?
4)?int?x?=?0x1234;?
5)?float?fl?=?1.2;?

Q36?Which?of?the?following?are?valid?statements?regarding?the?following?piece?of?code??
1.?String?s1?=?"abcd";?
2.?StringBuffer?sb1?=?new?StringBuffer("abcd");?
3.?int?val?=?6;?
4.?System.out.println(s1?+?val);?
5.?System.out.println(sb1?+?val);?

1)?The?text?"abcd6"?is?displayed?followed?by?"abcd6".?
2)?The?code?fails?to?compile?because?String?conversion?does?not?apply?to?StringBuffer.?
3)?The?code?compiles?but?upon?execution,?throws?a?NullPointerException?at?line?5.?
4)?The?code?fails?to?compile?at?line?2,?because?this?is?not?a?valid?way?to?create?a?StringBuffer.?
5)?The?code?fails?to?compile?at?line?1,?because?this?is?not?a?valid?way?to?create?a?String.?

Q37?True?or?False.?
Abstract?methods?can?be?declared?as?static.?
1)?True?
2)?False?

Q38?FlowLayout?is?the?default?layout?manager?for?which?of?the?following?containers:?
1)?Panel?
2)?Applet?
3)?Frame?
4)?Window?
5)?Dialog?

Q39?In?which?class?are?the?following?methods?defined:?
-?wait()?
-?notify()?
-?notifyAll()?
1)?Thread?
2)?Runnable?
3)?Object?
4)?Event?
5)?Synchronize?

Q40?Which?one?of?the?following?creates?an?instance?of?Vector?with?an?initial?capacity?of?10,?and?an?incremental?capacity?of?5.?
1)?new?Vector(10,?5);?
2)?new?Vector(5,10);?
3)?None.?There?is?no?constructor?of?Vector?which?provides?this?feature.?
4)?Vector?is?declared?as?final,?and?it?is?therefore?not?possible?to?instantiate?it.?

Q41?True?of?False.?
CheckboxGroup?is?a?subclass?of?Component.?
1)?True?
2)?False?

Q42?Which?statements(s)?below?are?true?about?the?following?piece?of?code.?
class?Test?implements?Runnable{?
public?static?void?main(String?[]?args){?
Thread?t?=?new?Thread(new?Test());?
t.start();?
}?

public?void?run(int?limit){?
for?(int?x?=?0;?x?<?limit;?x++)?
System.out.println(x);?
}?
}?

1)?All?the?numbers?up?to?(but?not?including)?"limit"?are?printed?out.?
2)?Nothing?is?displayed.?There?is?no?explicit?call?to?the?run()?method.?
3)?The?code?fails?to?compile?because?the?Runnable?interface?is?not?implemented?correctly.?
4)?The?code?can?be?made?to?compile?by?declaring?the?class?Test?to?be?abstract.?
5)?The?code?can?be?made?to?compile?by?removing?the?words?"implements?Runnable".?

Q43?Consider?the?following?code?and?select?the?statement(s)?which?are?true:?
1.?class?Test?extends?Frame{?
2.?
3.?public?static?void?main(String?[]?args){?
4.?Test?t?=?new?Test();?
5.?}?
6.?
7.?Test(){?
8.?Button?b?=?new?Button("Hello");?
9.?add(b,?BorderLayout.SOUTH);?
10.?}?
11.?
12.?}?

1)?The?code?compiles.?When?executed,?nothing?is?displayed.?
2)?The?code?compiles.?When?executed,?a?button?with?the?text?"Hello"?is?located?at?the?bottom?on?the?screen.?The?button?is?as?tall?as?the?text,?but?is?the?width?of?the?frame.?
3)?Adding?in?the?following?two?lines?between?lines?9?and?10?will?display?a?frame?with?a?button?at?the?bottom?of?the?frame:?setSize(100,?100);?setVisible(true);?
4)?The?code?fails?to?compile,?because?a?layout?manager?was?not?specified.?
5)?The?code?fails?to?compile?because?you?cannot?subclass?the?Frame?class.?

Q44?Before?which?of?the?following?can?the?keyword?"synchronized"?be?placed,?without?causing?a?compile?error.?
1)?class?methods?
2)?instance?methods?
3)?any?block?of?code?within?a?method?
4)?variables?
5)?a?class?

Q45?Consider?the?following?class?definitions:?
class?Base{}?
class?Subclass1?extends?Base{}?
class?Subclass2?extends?Base();?
Now?consider?the?following?declarations:?
Base?b?=?new?Base();?
Subclass1?s1?=?new?Subclass1();?
Subclass2?s2?=?new?Subclass2();?
Now,?consider?the?following?assignment:?
s1?=?(Subclass1)s2;?
Which?of?the?following?statements?are?correct?regarding?this?assignment?(select?one).?
1)?The?assignment?is?legal?and?compiles?without?an?error.?No?exception?is?thrown?at?runtime.?
2)?The?code?fails?to?compile.?The?compiler?complains?that?the?assignment?"s1?=?(Subclass1)s2"?is?illegal.?
3)?The?code?compiles?but?ClassCastException?is?thrown?at?runtime.?
4)?The?code?fails?to?compile.?You?cannot?subclass?a?parent?class?more?than?once.?

Q46?Select?all?the?valid?ways?of?initialising?an?array.?
1)?int?x[]?=?{1,2,3};?
2)?int?[]x[]?=?{{1,2,3},{1,2,3}};?
3)?int?x[3]?=?{1,2,3};?
4)?int?[]x?=?{0,0,0};?
5)?char?c[]?=?{'a',?'b'};?

Q47?What?is?the?valid?declaration?for?the?finalize()?method.?
1)?protected?void?finalize()?throws?Throwable?
2)?final?finalize()?
3)?public?final?finalize()?
4)?private?boolean?finalize()?
5)?private?final?void?finalize()?throws?Exception?

Q48?What?is?the?method?used?to?retrieve?a?parameter?passed?into?an?applet?using?the?PARAM?tag.?
1)?getParam()?
2)?getParameter()?
3)?getVariable()?
4)?getVar()?
5)?There?is?no?method?available.?You?must?use?"String?[]?args"?approach.?

Q49?You?have?a?button,?which?is?in?a?panel.?The?panel?is?inside?a?frame.?You?assign?the?Frame?a?24-point?font?and?a?background?colour?of?yellow.?You?set?the?panel?to?have?a?background?colour?of?red.?Which?of?the?following?statements?are?true?(select?all?valid?statements).?
1)?The?font?size?of?the?button?is?24-point.?
2)?The?background?colour?of?the?button?is?the?same?as?that?of?the?frame.?
3)?The?panel?has?a?font?size?of?8-point.?
4)?The?button?inherits?the?font?from?the?panel.?
5)?This?is?not?a?valid?configuration.?It?is?not?valid?to?place?a?panel?into?a?frame.?

Q50?Consider?the?following?piece?of?code?and?select?the?correct?statement(s):?
public?class?Test{?
final?int?x?=?0;?
Test(){?
x?=?1;?
}?
final?int?aMethod(){?
return?x;?
}?
}?

1)?The?code?fails?to?compile.?The?compiler?complains?because?there?is?a?final?method?("aMethod")?in?a?non-final?class.?
2)?The?code?compiles?correctly.?On?execution,?an?exception?is?thrown?when?the?Test()?constructor?is?executed.?
3)?The?code?fails?to?compile?because?an?attempt?is?made?to?alter?the?value?of?a?final?variable.?
4)?Removing?the?"final"?keyword?from?the?line?"final?int?x?=?0"?will?allow?the?code?to?compile?correctly.?
5)?The?code?fails?to?compile?because?only?methods?can?be?declared?as?final?(and?therefore?"final?int?x?=?0"?is?not?valid).?

Q51?What?is?displayed?when?the?following?code?fragment?is?compiled?and?executed?(assume?that?the?enveloping?class?and?method?is?correctly?declared?and?defined):?
StringBuffer?sb1?=?new?StringBuffer("abcd");?
StringBuffer?sb2?=?new?StringBuffer("abcd");?
String?s1?=?new?String("abcd");?
String?s2?=?"abcd";?
System.out.println(s1==s2);?
System.out.println(s1=s2);?
System.out.println(sb1==sb2);?
System.out.println(s1.equals(sb1));?
System.out.println(sb1.equals(sb2));?

1)?The?code?fails?to?compile,?complaining?that?the?line?System.out.println(s1=s2);?is?illegal.?
2)?The?code?fails?to?compile?because?the?equals()?method?is?not?defined?for?the?StringBuffer?class.?
3)?false?
true?
true?
false?
false?
4)?false?
abcd?
false?
false?
false?
5)?false?
true?
false?
false?
true?

Q52?What?is?the?default?layout?manager?for?applets?and?panels??
1)?FlowLayout?
2)?BorderLayout?
3)?GridBagLayout?
4)?GridLayout?
5)?None?of?these?

Q53?Which?of?the?following?statements?will?compile?without?an?error??
1)?Boolean?b?=?new?Boolean("abcd");?
2)?float?f?=?123;?
3)?byte?b?=?127;?
4)?int?x?=?(int)(1.23);?
5)?short?s?=?128;?

Q54?True?or?False.?
Menus?can?be?added?to?containers.?
1)?True?
2)?False?

Q55?Which?of?the?following?statements?are?true?regarding?the?graphical?methods?
paint(),?repaint()?and?update().?
1)?paint()?schedules?a?call?to?repaint().?
2)?repaint()?schedules?a?call?to?update().?
3)?update()?calls?paint().?
4)?update()?schedules?a?call?to?repaint().?
5)?repaint()?calls?paint()?directly.?

Q56?To?which?of?the?following?can?a?menubar?component?be?added??
1)?Applet?
2)?Panel?
3)?Frame?
4)?Canvas?

Q57?With?regard?to?apply?applet?by?HTML?tags,?which?of?the?following?statements?are?correct??
1)?The?CODE,?WIDTH?and?HEIGHT?tags?are?mandatory?and?the?order?is?insignificant.?
2)?CODE?and?CODEBASE?are?case?insensitive,?and?the?.class?extension?is?optional.?
3)?The?PARAM?tag?is?case?insensitive.?
4)?It?is?possible?to?download?multiple?JAR's?with?the?ARCHIVE?tag?(eg,?ARCHIVE?=?"a.jar,?b.jar").?
5)?The?CODE?tag?is?the?only?mandatory?tag.?

Q58?Consider?the?following?piece?of?code?and?select?the?correct?statements.?
1.?Object?o?=?new?String("abcd");?
2.?String?s?=?o;?
3.?System.out.println(s);?
4.?System.out.println(o);?

1)?The?following?is?displayed:?
abcd?
abcd?
2)?The?code?fails?to?compile?at?line?1.?
3)?The?code?fails?to?compile?at?line?2?
4)?The?code?fails?to?compile?at?line?4.?
5)?The?code?can?be?made?to?compile?by?changing?line?1?to?the?following:?
String?o?=?new?String("abcd");?

Q59?Which?of?the?following?are?legal?methods?for?the?String?class??
1)?length()?
2)?toUpper()?
3)?toUpperCase()?
4)?toString()?
5)?equals()?

Q60?What?is?the?output?from?the?following?piece?of?code:?
loop1:?
for(int?i?=?0;?i?<?3;?i++){?
loop2:?
for(int?j?=?0;?j?<?3;?j++){?
if?(i?==?j){?
break?loop2;?
}?
System.out.print("i?=?"?+?i?+?"?j?=?"?+?j?+?"?");?
}?
}?

1)?
i?=?1?
j?=?0?
2)?
i?=?1?
j?=?0?
i?=?2?
j?=?1?
3)?i?=?0?
j?=?1?
i?=?0?
j?=?2?
i?=?1?
j?=?0?
i?=?2?
j?=?0?
i?=?2?
j?=?1?
4)?i?=?1?
j?=?0?
i?=?2?
j?=?0?
i?=?2?
j?=?1?
5)?
i?=?1?j?=?0?i?=?2?j?=?0?i?=?2?j?=?1?

Q61?What?is?displayed?when?the?following?piece?of?code?is?executed:?
loop1:?
for(int?i?=?0;?i?<?3;?i++){?
loop2:?
for(int?j?=?0;?j?<?3;?j++){?
if?(i?==?j){?
continue?loop2;?
}?
System.out.println("i?=?"?+?i?+?"?j?=?"?+?j);?
}?
}?

1)?i?=?0?j?=?0?
i?=?0?j?=?1?
i?=?1?j?=?0?
i?=?1?j?=?1?
i?=?2?j?=?0?
i?=?2?j?=?1?
2)?i?=?0?j?=?0?
i?=?1?j?=?1?
i?=?2?j?=?2?
3)?i?=?0?j?=?1?
i?=?0?j?=?2?
i?=?1?j?=?0?
i?=?1?j?=?2?
i?=?2?j?=?0?
i?=?2?j?=?1?
4)?None?of?the?above.?

Q62?Consider?the?following?piece?of?code,?and?select?the?correct?statement(s):?
long?val?=?2;?
...?
...?
Switch?(val){?
default:?
System.out.println("Default");?
break;?
case?1:?
System.out.println("1");?
break;?
case?2:?
System.out.println("2");?
case?3:?
System.out.println("3");?
break;?
}?

1)?The?following?is?displayed:?
2?
3?
2)?The?following?is?displayed:?
2?
3)?The?code?fails?to?compile?because?the?default?case?must?be?the?last?case?in?the?switch?statement.?
4)?The?code?fails?to?compile?because?the?argument?for?a?switch?statement?cannot?be?a?variable?of?type?long.?
5)?The?following?is?displayed:?
2?
3?
Default?

Q63?Consider?the?following?piece?of?code,?and?select?the?correct?statement(s):?
public?class?Test?extends?Applet{?
public?void?init(){?
setLayout(new?GridLayout(1,2));?
add(new?Button("#1"));?
add(new?Button("#2"));?
add(new?Button("#3"));?
add(new?Button("#4"));?
}?
}?

1)?The?Gridlayout?is?created?with?1?row?and?2?columns.?
2)?Adding?the?button?with?the?label?"#3"?will?cause?an?exception?to?be?thrown.?
3)?Adding?the?button?with?label?"#3"?will?cause?it?to?overwrite?the?button?with?label?"#2".?
4)?The?layout?automatically?extends?to?accommodate?the?additional?buttons.?
5)?Only?2?buttons?are?displayed,?one?with?label?"#1"?and?one?with?label?"#4".?

Q64?Which?of?the?following?layout?managers?will?retain?the?preferred?width?and?height?of?the?contained?components.?
1)?GridLayout?
2)?GridBagLayout?
3)?BoxLayout?
4)?FlowLayout?
5)BorderLayout?

Q65?You?construct?a?List?by?calling?List(5,?false).?
Which?statements?below?are?correct?(assume?the?layout?managers?do?not?modify?the?List?properties).?
1)?The?list?supports?multiple?selection.?
2)?The?list?has?5?visible?items.?
3)?A?vertical?scroll?bar?will?be?added?automatically?if?needed.?
4)?The?code?fails?to?compile.?The?given?constructor?is?not?a?valid?one.?

Q66?Which?of?the?following?will?definitely?stop?a?thread?from?executing:?
1)?wait()?
2)?notify()?
3)?yield()?
4)?suspend()?
5)?sleep()?

Q67?Which?of?the?following?is?the?correct?method?to?call?to?change?the?layout?manager?for?a?container:?
1)?setLayoutManager()?
2)?setLayManager()?
3)?changeLayout()?
4)?You?can't?change?the?layout?manager?for?a?container.?
5)?setLayout()?

Q68?Which?is?the?correct?way?to?add?a?button,?referenced?by?b,?to?a?panel,?referenced?by?p.?
1)?add(p,?b);?
2)?p.add(b)?
3)?b.add(p)?
4)?Buttons?can't?be?added?to?panels.?
5)?add(p)?

Q69?What?is?displayed?when?the?following?code?is?compiled?and?executed:?
long?val?=?2;?
switch(val){?
case?1:?
System.out.println("1");?
case?2:?
System.out.println("2");?
default:?
System.out.println("default");?
}?
1)?default?
2)?2?
default?
3)?The?code?fails?to?compile?because?there?are?no?break?statements?in?the?case?clauses.?
4)?The?code?fails?to?compile?because?a?long?data?type?is?not?a?valid?parameter?for?a?switch?statement.?

Q70?What?is?displayed?following?the?execution?of?the?code?below:?
1.?class?Test{?
2.?String?s;?
3.?public?static?void?main(String?[]args){?
4.?int?x?=?4;?
5.?if?(x?<?4)?
6.?System.out.println("Val?=?"?+?x);?
7.?else?
8.?System.out.println(s);?
9.?}?
10.?}?

1)?Nothing.?The?code?doesn't?compile?because?the?variable?s?wasn't?initialised.?
2)?The?string?"null"?is?displayed.?
3)?The?code?runs,?but?a?NullPointerException?is?thrown?at?line?8.?
4)?The?code?compiles.?No?exception?is?thrown?but?nothing?is?displayed.?
5)?Nothing.?The?code?doesn't?compile?because?you?can't?make?a?static?reference?to?a?non-static?variable.?

Q71?Consider?the?following?piece?of?code:?
class?Test{?
int?x;?
String?s;?
float?fl;?
boolean?[]?b?=?new?boolean?[5];?

public?static?void?main(String?[]args){?
System.out.println(x);?
System.out.println(s);?
System.out.println(fl);?
System.out.println(b[2]);?
}?
}?
What?is?displayed?when?this?code?is?executed.?
1)?0?
null?
0.0?
false?
2)?0?
"?"?
0.0?
true?
3)?Nothing.?The?code?fails?to?compile?because?the?boolean?array?is?incorrectly?declared.?
4)?Nothing.?The?code?will?not?compile?because?the?static?method?cannot?access?the?variables?since?there?is?no?instance?of?the?Test?class.?

Q72?What?is?displayed?when?the?following?code?is?compiled?and?executed:?
String?s?=?"abcd";?
String?s1?=?new?String(s);?
if?(s?==?s1)?
System.out.println("the?same");?
if?(s.equals(s1))?
System.out.println("equals");?
1)?the?same?
equals?
2)?equals?
3)?the?same?
4)?The?code?compiles,?but?nothing?is?displayed?upon?execution.?
5)?The?code?fails?to?compile.?

Q73?What?is?the?legal?range?for?the?byte?data?type:?
1)?0?to?+255?
2)?-127?to?+128?
3)?-128?to?+127?
4)?0?to?65535?
5)?-32767?to?+32768?

Q74?What?is?displayed?when?the?following?code?is?executed:?
String?s?=?"abcdef";?
System.out.println(s.charAt(4));?
1)?d?
2)?e?
3)?Nothing.?An?ArrayIndexOutOfBoundsException?is?thrown?
4)?The?code?does?not?compile.?charAt()?is?not?a?valid?method?of?the?String?class.?
5)?The?code?does?not?compile?because?the?string?s?is?not?created?correctly.?

Q75?True?or?False.?
The?String?class?does?not?have?an?append()?method.?
1)?True?
2)?False?

Q76?Consider?the?following?code?segment.?
double?d?=?-11.1;?
double?d1?=?method(d);?
System.out.println(d1);?
If?the?output?of?this?code?segment?is?-12.0,?then?what?methods?could?be?called?in?method()?above.?
1)?floor()?
2)?ceil()?
3)?round()?
4)?abs()?
5)?min()?

Q77?What?outputs?are?possible?from?invoking?Math.random().?
1)?-0.12?
0.56E3?
2)?0.12?
1.1E1?
3)?-23.45?
0.0?
4)?0.356?
0.03?
5)?1.00?
0.99?

Q78?In?a?thread,?the?wait()?method?must?be?called?inside?which?of?the?following:?
1)?A?while()?loop?
2)?The?run()?method?
3)?synchronised?code?
4)?The?constructor?
5)?It?doesn't?matter?where?the?wait()?is?called?from.?

Q79?Consider?the?following?piece?of?code:?
public?class?Test?extends?Applet{?
public?void?init(){?
setLayout(new?BorderLayout());?
add("South",?new?Button("B1"));?
add("North",?new?Button("B2"));?
add("South",?new?Button("B3"));?
}?
}?
Select?the?correct?statements?regarding?the?above.?
1)?There?are?2?buttons?displayed?in?the?SOUTH?section,?B1?and?B3.?
2)?Only?B3?is?displayed?in?the?SOUTH?section.?
3)?An?exception?is?thrown?when?an?attempt?is?made?to?add?a?second?component?to?SOUTH.?
4)?Only?B1?is?displayed?in?the?SOUTH?section.?
5)?You?can't?add?buttons?to?applets.?

Q80?What?is?displayed?when?the?following?piece?of?code?is?executed:?
1.?String?val?=?null;?
2.?int?x?=?Integer.parseInt(val);?
3.?
4.?System.out.println(x);?
1)?0?
2)?null?
3)?A?NumberFormatException?is?thrown?at?line?2.?
4)?Nothing?is?displayed?

Q81?Consider?the?following?piece?of?code:?
class?A{?
int?x?=?0;?
A(int?w){?
x?=?w;?
}?
}?

class?B?extends?A{?
int?x?=?0;?
B(int?w){?
x?=?w?+1;?
}?
}?
1)?The?code?compiles?correctly.?
2)?The?code?fails?to?compile,?because?both?class?A?and?B?do?not?have?valid?constructors.?
3)?The?code?fails?to?compile?because?there?is?no?default?no-args?constructor?for?class?A.?

Q82?Given?an?object?myListener?(whose?class?implements?the?ActionListener?interface),?which?of?the?following?are?valid?ways?to?enable?myListener?to?receive?all?action?events?from?component?smallButton??
1)?smallButton.add(myListener);?
2)?smallButton.addListener(myListener);?
3)?smallButton.addActionListener(myListener);?
4)?smallButton.addItem(myListener);?

Q83?Which?of?the?following?are?valid?listener?interfaces??
1)?ActionListener?
2)?MouseMotionListener?
3)?SystemEventListener?
4)?MouseClickListener?
5)?WindowListener?

Q84?Which?of?the?following?is?the?correct?way?to?set?the?foreground?colour?of?a?component,?c.?
1)?c.setForeground("red");?
2)?c.setColor("Color.red");?
3)?c.Foreground(Color.red);?
4)?c.setForegroundColor("red");?
5)?c.setForeground(Color.red);?

Q85?Which?of?the?following?are?valid?ways?to?create?a?Map?collection.?
1)?Map?m?=?new?Map();?
2)?Map?m?=?new?Map(init?capacity,?increment?capacity);?
3)?Map?m?=?new?Map(new?Collection());?
4)Map?is?an?interface,?and?cannot?be?instantiated.?

Q86?Select?all?the?correct?statements?relating?to?the?following?piece?of?code??
1.?public?class?A{?
2.?abstract?int?method();?
3.?void?anotherMethod(){?
4.?}?
5.?
6.?class?B?extends?A{?
7.?int?method(){?
8.?return?2;?
9.?}?
10.?}?
1)?Changing?"extends"?to?"implements"?on?line?6?will?allow?the?code?to?compile?correctly.?
2)?The?method()?in?class?A?cannot?be?abstract?without?the?entire?class?being?declared?as?abstract.?
3)?Declaring?class?A?to?be?abstract?will?allow?the?code?to?compile?correctly.?
4)?The?class?A?must?have?an?explicit?default?constructor?in?order?for?it?to?be?subclassed?correctly.?
5)?The?code?fails?to?compile,?because?class?B?does?not?implement?anotherMethod().?

Q87?Which?layout?manager?do?the?comments?below?refer?to:?
All?components?contained?in?it?have?the?same?width?and?height.?Contained?components?are?stretched?to?have?the?same?dimensions.?
1)?FlowLayout?
2)?BorderLayout?
3)?GridLayout?

Q88?Select?all?valid?statements.?
1)?When?typing?text?into?a?TextField,?scroll?bars?will?automatically?appear?when?the?TextField?becomes?full.?
2)?When?typing?text?into?a?TextArea,?scroll?bars?will?appear?when?text?is?typed?past?the?boundaries?of?the?TextArea.?
3)?TextFields?can?have?more?than?1?row?of?text.?
4)?The?class?TextArea?is?a?super?class?of?the?class?TextField.?
5)?Both?TextAreas?and?TextFields?have?a?method?called?setEditable(),?which?can?enable?or?disable?editing?of?the?component.?

Q89?In?which?class?is?the?paint()?method?defined??
1)?Object?
2)?Applet?
3)?Component?
4)?Thread?
5)?Graphics?

Q90?Select?the?statement?which?most?closely?describes?the?user?interface?of?an?applet?with?the?following?init()?method:?
public?void?init(){?
Panel?p?=?new?Panel();?
p.setLayout(new?BorderLayout());?
p.add(new?Button("Hello"),?BorderLayout.EAST);?
p.add(new?Button("Bye"),?BorderLayout.WEST);?
add(p);?
}?
1)?Two?buttons?are?displayed.?A?button?with?"Hello"?is?on?the?right?side?of?the?applet.?The?button?with?"Bye"?is?on?the?left?side?of?the?applet.?Both?buttons?extend?from?the?centre?of?the?applet?to?each?side,?and?are?the?height?of?the?applet.?
2)?Two?buttons?are?displayed.?A?button?with?"Hello"?is?on?the?right?side?of?the?applet.?The?button?with?"Bye"?is?on?the?left?side?of?the?applet.?Both?buttons?are?only?as?wide?as?the?text?on?the?button,?but?are?the?height?of?the?applet.?
3)?Two?buttons?are?displayed.?A?button?with?"Hello"?is?on?the?right?side?of?the?applet.?The?button?with?"Bye"?is?on?the?left?side?of?the?applet.?Both?buttons?are?only?large?enough?to?support?the?associated?button?texts.?

Q91?What?is?wrong?about?the?following?piece?of?code?(assume?the?relevant?import?statements?are?present):?
public?class?Test{?
public?static?void?main?(String?[]?args)?throws?IOException{?
if?(args[0]?==?"hello")?
throw?new?IOException();?
}?
}?
1)?Nothing.?The?code?compiles?correctly.?
2)?The?code?fails?to?compile.?You?can't?throw?an?exception?from?the?main()?method.?
3)?The?code?fails?to?compile.?IOException?is?a?system?exception,?and?cannot?be?thrown?by?application?code.?

Q92?Consider?the?following?piece?of?code,?and?select?the?statements?which?are?true.?
class?Test{?
int?x?=?5;?
static?String?s?=?"abcd";?
public?static?void?method(){?
System.out.println(s?+?x);?
}?
}?
1)?The?code?compiles?and?displays?"abcd5".?
2)?The?code?compiles,?but?throws?an?exception?at?runtime,?because?variable?x?isn't?declared?as?static.?
3)?The?code?fails?to?compile?because?you?can't?make?a?static?reference?to?a?non-static?variable.?
4)?The?code?will?compile?if?x?is?declared?to?be?static.?
5)?The?code?will?compile?by?removing?the?static?keyword?from?the?declaration?of?method().?

Q93?Select?all?legal?code?fragments?from?the?following.?
1)?char?c?=?"c";?
2)?Boolean?b?=?new?Boolean("qwerty");?
3)?String?s?=?"null";?
4)?int?q;?
for?(int?p?=?0,?q?=?0;?p?<?5;?p++){?
System.out.println("Val?=?"?+?p?+?q);?
}?
5)?int?x?=?3;?
Float?f?=?new?Float(x);?

Q94?Which?of?the?following?are?legal?ways?to?construct?a?RandomAccessFile??
1)?RandomAccessFile("file",?"r");?
2)?RandomAccessFile("r",?"file");?
3)?RandomAccessFile('r',?"file");?
4)?RandomAccessFile("file",?'r');?
5)?RandomAccessFile("file",?"rw");?

Q95?Consider?the?following?code?and?select?the?most?appropriate?statements.?
1.?class?Test{?
2.?public?int?doubleValue(int?a)?
3.?System.out.println(a);?
4.?return?(int)(a?*?2);?
5?}?
6.?
7?public?float?doubleValue(int?a){?
8.?System.out.println(a);?
9.?return?(float)(a?*?2);?
10.?}?
11.}?
1)?The?code?compiles?since?the?two?doubleVal()?methods?have?different?return?types.?
2)?The?code?doesn't?compile?because?the?compiler?sees?two?methods?with?the?same?signature.?
3)?The?code?can?be?made?to?compile?by?redefining?the?parameter?for?doubleVal()?on?line?7?to?be?"float?a"?instead?of?"int?a".?
4)?The?code?can?be?made?to?compile?by?replacing?the?public?declaration?on?line?7?with?private.?

Q96?What?is?displayed?when?the?following?piece?of?code?is?executed:?
class?Test?extends?Thread{?
public?void?run(){?
System.out.println("1");?
yield();?
System.out.println(2");?
suspend();?
System.out.println("3");?
resume();?
System.out.println("4");?
}?

public?static?void?main(String?[]args){?
Test?t?=?new?Test();?
t.start();?
}?
}?
1)?1?
2?
3?
4?
2)?1?
2?
3?
3)?1?
2?
4)?Nothing.?This?is?not?a?valid?way?to?create?and?start?a?thread.?
5)?1?

Q97?Consider?the?following?piece?of?code,?and?select?the?most?appropriate?statements.?
TextField?t?=?new?TextField("Hello",?20);?
1)?The?user?will?be?able?to?edit?the?string.?
2)?The?field?will?be?20?characters?wide.?
3)?The?text?field?will?be?same?size?on?all?platforms,?since?Java?is?platform?independent.?
4)?When?entering?text?into?the?field,?only?20?characters?can?be?entered.?
5)?If?the?font?is?changed,?the?size?of?the?textfield?will?adjust?to?allow?20?characters?to?be?displayed.?

Q98?True?of?False.?
Using?the?instanceof?operator?on?an?interface?will?cause?a?runtime?exception.?
1)?True?
2)?False?

Q99?Which?of?the?following?are?valid?ways?to?create?a?Button?component??
1)?new?Button();?

2)?new?Button(30,?10);?where?30?is?the?width?of?the?button?and?10?is?the?height?
3)?new?Button("hello");?
4)?new?Button(new?String("hello"));?
5)?new?Button(String("hello"));?

Q100?Which?of?the?following?are?NOT?valid?subclasses?of?AWTEvent??
1)?MouseClickEvent?
2)?OutputEvent?
3)?MouseMotionEvent?
4)?KeyAdapter?
5)?WindowMinimizeEvent?

Q101?Which?of?the?following?are?valid?methods?for?the?Graphics?class??
1)?drawOval(int?x,?int?y,?int?width,?int?height)?
2)?toString()?
3)?drawArc(int?x,?int?y,?int?width,?int?height,?int?startAngle,?int?arcAngle)?
4)?drawPolygon(int[]?xPoints,?int[]?yPoints,?int?nPoints)?
5)?fillArc(int?x,?int?y,?int?width,?int?height,?int?startAngle,?int?arcAngle)?

Q102?Which?of?the?following?are?valid?methods?in?the?Math?class??
1)?arcTan(double?a)?
2)?atan(double?a)?
3)?sqrt(double?a)?
4)?min(int?a,?int?b)?
5)?cosine(double?a)?

Q103?Which?of?the?following?will?display?the?string?"ica",?given:?
String?s?=?"Metallica";?
1)?System.out.println(s.subString(7));?
2)?System.out.println(s.substring(6));?
3)?System.out.println(s.subString(6,?8));?
4)?System.out.println(s.substring(7,?9));?
5)?None?of?these.?

Q104?Which?of?the?following?are?defined?in?the?Object?class??
1)?toString()?
2)?equals(Object?o)?
3)?public?static?void?main(String?[]?args)?
4)?System.out.println()?
5)?wait()?

Q105?Select?all?valid?statements?relating?to?the?paint()?method?defined?in?the?Component?class.?
1)?It?takes?4?int?types?as?parameters,?representing?the?x?and?y?co-ordinates,?width?and?height,?respectively.?
2)?It?is?declared?as?final,?and?so?it?cannot?be?overridden.?
3)?It?is?declared?as?static.?
4)?It?takes?an?instance?of?the?Graphics?component?as?a?parameter.?
5)?When?overriding?the?paint()?method,?you?must?handle?the?identification?and?repair?of?damaged?components.?

Q106?Which?of?the?following?keywords?can?be?applied?to?a?method??
1)?transient?
2)?volatile?
3)?private?
4)?protected?
5)?final?

Q107?Which?of?the?following?keywords?can?be?applied?to?a?top-level?class?(i.e.,?not?an?inner?class)??
1)?private?
2)?protected?
3)?transient?
4)?public?
5)?final?

Q108?Consider?the?following?piece?of?code,?and?select?all?relevant?statements:?
1.?class?Test{?
2.?public?static?void?main(String?[]?args){?
3.?aMethod();?
4.?}?
5.?
6.?static?void?aMethod(){?
7.?try{?
8.?System.out.println("abcd");?
9.?return;?
10.?}?finally?{?
11.?System.out.println("1234");?
12.?}?
13.?}?
14.}?

1)?An?exception?is?thrown?at?line?9.?
2)?The?code?fails?to?compile.?The?compiler?complains?about?the?return?statement?at?line?9.?
3)?abcd?
1234?
4)?abcd?
5)?The?code?fails?to?compile,?complaining?that?a?'catch'?clause?is?missing?from?line?10.?

Q109?Which?of?the?following?statements?are?true.?
1)?The?type?"int"?is?a?32-bit?signed?integer?value.?
2)?The?type?"short"?is?a?16-bit?unsigned?integer?value.?
3)?The?type?"char"?is?a?16-bit?Unicode?character.?
4)?The?type?"float"?is?a?64-bit?floating?point?value.?
5)?The?type?"long"?is?a?64-bit?signed?integer?value.?

Q110?Which?layout?manager?is?described?by?the?following:?
It?aligns?components?vertically?and?horizontally,?without?requiring?that?the?components?be?of?the?same?size.?It?maintains?a?dynamic?rectangular?grid?of?cells,?with?each?component?occupying?one?or?more?cells,?called?its?display?area.?
1)?GridLayout?
2)?FlowLayout?
3)?GridBagLayout?
4)?BoxLayout?

Q111?True?of?False.?
The?StringBuffer?class?overrides?the?toString()?method?to?return?a?String?representation?of?the?StringBuffer.?
1)?True?
2)?False?

Q112?Select?the?correct?statements?from?the?following:?
1)?The?class?RandomAccessFile?is?a?subclass?of?the?java.io.File?class.?
2)?The?class?java.io.FileWriter?contains?methods?to?write?primitives?(eg,?writeInt(),?writeFloat(),?etc)?
3)?The?class?java.io.BufferedOutputStream?contains?methods?to?write?primitives?(eg,?writeInt(),?writeFloat(),?etc)?
4)?The?File?class?defines?a?method?which?can?be?used?to?delete?files?and?directories?from?a?disk.?
5)?The?RandomAccessFile?class?defines?a?method?which?can?be?used?to?delete?files?and?directories?from?a?disk.?

Q113?True?or?False.?
A?class?can?implement?more?than?one?interface,?but?can?only?inherit?from?a?single?parent?class.?
1)?True?
2)?False?

Q114?What?is?the?result?of?compiling?and?executing?the?following?code.?
public?class?ThreadTest?extends?Thread?{?
public?void?run()?{?
System.out.println("In?run");?
yield();?
System.out.println("Leaving?run");?
}?

public?static?void?main(String?args?[])?{?
(new?ThreadTest()).start();?
}?
}?
1)?The?code?fails?to?compile?in?the?main()?method.?
2)?The?code?fails?to?compile?in?the?run()?method.?
3)?Only?the?text?"In?run"?will?be?displayed.?
4)?The?text?"In?run"?followed?by?"Leaving?run"?will?be?displayed.?
5)?The?code?compiles?correctly,?but?nothing?is?displayed.?

Q115?Which?of?the?following?will?compile?without?errors.?
1)?Byte?b?=?new?Byte(123);?
2)?Byte?b?=?new?Byte("123");?
3)?Byte?b?=?new?Byte();?
b?=?123;?
4)?Byte?b?=?new?Byte((int)123.4);?
5)?Byte?b?=?new?Byte(0x123);?

Q116?Consider?the?following?piece?of?code?and?select?the?correct?statement(s):?
1.?public?class?Test{?
2.?static?int?x;?
3.?static?public?void?main(String?[]?args){?
4.?x?=?x?+?1;?
5.?System.out.println("Value?is?"?+?x);?
6.?}?
7.?}?
1)?The?code?fails?to?compile.?The?compiler?complains?that?the?variable?x?is?used?before?it?is?initialised.?
2)?The?code?compiles?correctly?and?displays?"Value?is?1"?when?executed.?
3)?The?code?compiles?correctly,?but?throws?a?NullPointerException?at?line?5.?
4)?The?code?fails?to?compile?because?the?'main'?method?is?incorrectly?declared.?

Q117?Which?of?the?following?are?termed?"short?circuit"?logical?operators.?
1)?&?
2)?&&?
3)?|?
4)?||?
5)?^?

Q118?Which?of?the?following?are?valid?expressions.?
1)?Object?o?=?new?String("abcd");?
2)?Boolean?b?=?true;?
3)?Panel?p?=?new?Frame();?
4)?Applet?a?=?new?Panel()?
5)?Panel?p?=?new?Applet()?

Q119?Which?of?the?following?is?a?valid?way?to?declare?an?abstract?method?which?is?intended?to?be?public.?
1)?public?abstract?method();?
2)?public?abstract?void?method();?
3)?public?abstract?void?method(){}?
4)?public?virtual?void?method();?
5)?public?void?method()?implements?abstract;?

Q120?Which?of?the?following?are?valid?ways?to?define?a?constructor?for?class?Test.?
1)?public?void?Test(){}?
2)?public?Test(){}?
3)?private?Test(){}?
4)?public?static?Test(){}?
5)?final?Test(){}?

Q121?Which?of?the?following?statements?are?valid?for?a?method?which?is?overriding?the?following:?
protected?void?method(int?x){..}?
1)?The?overriding?method?must?take?an?int?as?its?only?parameter.?
2)?The?overriding?method?must?return?a?void.?
3)?The?overriding?method?can?be?declared?as?private.?
4)?The?overriding?method?can?return?any?value?it?wishes.?

Q122?True?or?False.?
An?inner?class?can?implement?an?interface?or?extend?a?class.?
1)?True?
2)?False?

Q123?Which?of?the?following?are?valid?return?types?for?listener?methods.?
1)?boolean?
2)?void?
3)?An?object?of?type?Event?
4)?An?object?of?type?Object?
5)?A?long?value,?representing?the?Object?ID.?

Q124?Consider?the?following?piece?of?code?and?select?the?correct?statements.?
1.?public?class?Test{?
2.?public?static?void?main(String?[]?args){?
3.?print();?
4.?}?
5.?
6.?public?static?void?print(){?
7.?System.out.println("Test");?
8.?}?
9.?
10.?public?void?print(){?
11.?System.out.println("Another?Test");?
12?}?
13.?}?
1)?The?code?compiles?successfully?and?displays?"Test".?
2)?Changing?the?code?at?line?10?to?the?following,?will?allow?the?code?to?compile?correctly:?
public?void?print(int?x){?
3)?The?code?fails?to?compile.?The?compiler?complains?about?a?static?reference?to?a?non-static?method,?print().?
4)?The?code?fails?to?compile.?The?compiler?complains?about?duplicate?methods.?
5)?Changing?the?return?type?on?line?10?from?'void'?to?'int'?will?allow?the?code?to?compile?correctly.?

Q125?Consider?the?following?list?of?tags?and?attributes?of?tags?and?select?the?ones?which?can?legally?be?placed?between?the?APPLET?and?/APPLET?delimiters.?
1)?JAVAC?
2)?JAR?
3)?CODE?
4)?NAME?
5)?PARAM?

Q126?Which?variables?can?an?inner?class?access?from?the?class?which?encapsulates?it.?
1)?All?static?variables?
2)?All?final?variables?
3)?All?instance?variables?
4)?Only?final?instance?variables?
5)?Only?final?static?variables?

Q127?Using?a?FlowLayout?manager,?which?of?the?following?is?the?correct?way?to?add?a?conponent?referenced?by?the?variable?"c"?to?a?container:?
1)?add(c);?
2)?add("Center",?c);?
3)?c.add();?
4)?c.set();?
5)?set(c);?

Q128?Assuming?there?is?a?class?X?which?implements?the?ActionListener?interface.?
Which?method?should?be?used?to?register?this?with?a?Button??
1)?addListener(new?X());?
2)?addActionListener(new?X());?
3)?addButtonListener(new?X());?
4)?addActionAdapter(new?X());?
5)?(new?X()).addActionListener();?

Q129?What?is?the?result?of?compiling?and?executing?the?following?fragment?of?code:?
boolean?flag?=?false;?
if?(flag?=?true)?
{?
System.out.println("true");?
}?
else?
{?
System.out.println("false");?
}?
1)?The?code?fails?to?compile?at?the?"if"?statement.?
2)?An?exception?is?thrown?at?run-time?at?the?"if"?statement.?
3)?The?text?"true"?is?displayed.?
4)?The?text?"false"?is?displayed.?
5)?Nothing?is?displayed.?

Q130?Which?of?the?following?is?not?a?subclass?of?java.awt.Component??
1)?Frame?
2)?Container?
3)?CheckboxGroup?
4)?Canvas?
5)?Applet?

Q131?What?is?the?result?when?the?following?piece?of?code?is?compiled?and?executed.?
1.?public?class?Calc?{?
2.?public?static?void?main?(String?args?[])?{?
3.?int?total?=?0;?
4.?
5?.?for?(int?i?=?0,?j?=?10;?total?<?30;?++i,?--j)?{?
6.?System.out.println("?i?=?"?+?i?+?"?:?j?=?"?+?j);?
7.?
8.?total?+=?(i?+?j);?
9.?
10.?}?
11.?
12.?System.out.println("Total?"?+?total);?
13.?}?
14.?}?
1)?The?code?fails?to?compile?at?line?5,?because?the?variable?"j"?is?not?declared?correctly.?
2)?The?code?fails?to?compile?at?line?2,?because?you?can't?have?a?static?method?in?a?non-static?class.?
3)?The?code?compiles?correctly,?but?throws?an?exception?at?line?5.?
4)?The?code?compiles?correctly?but?throws?an?exception?at?line?2.?
5)?The?code?compiles?correctly?and?displays?the?following?when?executed:?
i?=?0?:?j?=?10?
i?=?1?:?j?=?9?
i?=?2?:?j?=?8?
Total?30?

Q132?Which?of?the?following?will?create?a?TextField?capable?of?displaying?10?characters,?with?the?initial?text?"hello"??
1)?TextField?t?=?new?TextField("hello",?10);?
2)?TextField?t?=?new?TextField(10,?"hello");?
3)?TextField?t?=?new?TextField();?
t.setCols(10);?
t.setText("hello");?
4)?TextField?t?=?new?TextField();?
t.setFieldSize(10);?
t.setText("hello");?
5)?None?of?the?above.?

Q133?What?is?the?effect?of?adding?the?sixth?element?to?a?Vector?created?using?the?following?code:?
new?Vector(5,?10);?
1)?An?IndexOutOfBounds?exception?is?thrown.?
2)?The?vector?grows?in?size?to?a?capacity?of?10?elements.?
3)?The?vector?grows?in?size?to?a?capacity?of?15?elements.?
4)?Nothing.?The?Vector?will?have?grown?when?the?fifth?element?was?added,?because?Vector?elements?are?zero-based.?
5)?Nothing.?This?is?not?a?valid?way?to?create?a?Vector.?

Q134?When?is?the?text?"Hi?there"?displayed??
public?class?StaticTest?{?
static?{?
System.out.println("Hi?there");?
}?

public?void?print()?{?
System.out.println("Hello");?
}?

public?static?void?main(String?args?[])?{?
StaticTest?st1?=?new?StaticTest();?
st1.print();?
StaticTest?st2?=?new?StaticTest();?
st2.print();?
}?
}?
1)?Never.?
2)?Each?time?a?new?object?of?type?StaticTest?is?created.?
3)?Once?when?the?class?is?loaded?into?the?Java?virtual?machine.?
4)?Only?when?the?main()?method?is?executed.?

Q135?Which?of?the?following?are?valid?ways?to?assign?the?value?of?5?to?a?variable?of?type?"int"?called?testValue??
1)?int?testValue?=?0x5;?
2)?int?testValue?=?(int)(2.1F?+?3.4D);?
3)?int?testValue?=?(octal)5;?
4)?int?testValue?=?(0x0A?>>?1);?
5)?int?testValue?=?(0x0A?>>>?1);?

Q136?Which?of?the?following?operations?will?cause?an?ActionEvent?to?be?generated.?
1)?Clicking?a?checkbox.?
2)?Selecting?an?option?from?a?Choice?box.?
3)?Scrolling?a?scroll?bar.?
4)?Clicking?a?button.?
5)?Hitting?ENTER?when?typing?in?a?text?field.?

Q137?True?or?False.?
All?Listener?interfaces?methods?are?declared?as?public?and?void.?
1)?True?
2)?False?
Q138?True?or?False.?
In?a?GridLayout,?the?width?and?height?of?all?cells?are?the?same.?
1)?True?
2)?False?

Q139?True?or?False.?
The?BorderLayout?manager?only?allows?a?single?component?to?be?displayed?in?each?sector.?
1)?True?
2)?False?

Q140?You?want?to?extend?the?functionality?of?the?String?class,?and?decide?that?the?best?approach?is?to?subclass?String.?Which?of?the?following?statements?are?correct.?
1)?The?approach?fails,?because?the?String?class?is?declared?as?final?and?cannot?be?subclassed.?
2)?The?approach?succeeds,?and?it?is?therefore?possible?to?override?the?standard?functionality?provided?by?String.?
3)?The?approach?fails,?because?the?String?class?is?declared?as?abstract,?and?therefore?it?cannot?be?subclassed.?

Q141?Which?of?the?following?are?valid?ways?to?determine?the?number?of?elements?in?an?array?defined?as?follows:?
int?intArray[]?=?{1,2,3};?
1)?intArray.size;?
2)?intArray.size();?
3)?intArray.length;?
4)?intArray.length();?
5)?intArray.getSize();?

Q142?You?have?a?check?box?within?a?panel,?and?the?panel?is?contained?within?an?applet.?There?are?no?other?components?within?the?applet.?
Using?"setBackground(Color.white)",?you?assign?the?background?colour?of?the?applet?to?white.?
Which?of?the?following?statements?are?true.?
1)?The?background?colour?of?the?panel?is?white.?
2)?The?foreground?colour?of?the?checkbox?is?the?same?as?the?foreground?colour?of?the?applet.?
3)?It?is?impossible?to?determine?the?background?colour?of?the?checkbox?from?the?imformation?supplied.?
4)?You?can't?put?a?panel?inside?an?applet.?

Q143?Which?of?the?following?can?be?added?to?a?menu??
1)?A?panel?
2)?A?button?
3)?A?menu?
4)?A?checkbox?
5)?A?menubar?

Q144?You?construct?an?application?by?making?the?following?call:?
Frame?app?=?new?Frame();?
app.setSize(100,100);?
Which?of?the?following?statements?are?correct.?
1)?An?empty?frame?of?size?100x100?is?displayed,?located?in?the?top?left?corner?of?the?screen.?
2)?An?empty?frame?of?size?100x100?is?displayed,?located?in?the?centre?of?the?screen.?
3)?Nothing?is?displayed.?There?is?no?setSize()?method?in?the?Frame?class.?
4)?Nothing?is?displayed.?The?frame?will?only?be?displayed?by?setting?the?forground?and?background?colours.?
5)?Nothing?is?displayed.?A?frame?is?created?by?default?with?zero?size,?and?invisible.?

Q145?Which?of?the?following?are?valid?methods?in?the?java.awt.Graphics?class??
1)?drawString()?
2)?drawOval()?
3)?fillRect()?
4)?drawPolyline()?
5)?fillPolyline()?

Q146?Which?of?the?following?are?valid?command?line?options?for?the?JAR?utility:?

1)?c?(create?a?new?or?empty?archive)?
2)?m?(indicates?that?first?argument?is?the?name?of?a?user-supplied?manifest)?
3)?M?(do?not?create?a?manifest)?
4)?z?(ZIP?the?contents?of?the?archive)?
5)?L?(list?the?archive?contents)?

Q147?Consider?the?following?code?segment?and?select?the?correct?statement(s):?
1.?class?FinalTest{?
2.?final?int?q;?
3.?final?int?w?=?0;?
4.?
5.?FinalTest(){?
6.?q?=?1;?
7.?}?
8.?
9.?FinalTest(int?x){?
10.?q?=?x;?
11.?}?
12.?}?
1)?The?code?fails?to?compile?because?a?class?cannot?have?more?than?1?constructor.?
2)?The?code?fails?to?compile?because?the?class?FinalTest?has?no?constructors.?
3)?The?code?fails?to?compile?because?the?an?attempt?is?made?to?initialise?a?final?variable?at?lines?6?and?10.?
4)?The?code?compiles?correctly?without?any?warnings?or?errors.?
5)?The?code?fails?to?compile?because?the?final?variable?q?is?not?initialised?correctly?at?line?2.?

Q148?True?or?False.?
It?is?valid?to?throw?(and?re-throw)?an?exception?inside?a?catch{}?clause.?
For?example:?
...?
catch?(Exception?e){?
throw?e;?
}?
1)?True?
2)?False?

Q149?True?or?False.?
A?scrollbar?will?appear?in?a?TextField?if?more?text?is?typed?than?can?be?displayed?within?the?TextField.?
1)?True?
2)?False?

Q150?True?or?False.?
It?is?valid?to?declare?an?inherited?method?as?abstract.?
1)?True?
2)?False?

Q151?Consider?the?following?code?segments?and?select?the?correct?statement:?
Segment?1:?
1.?int?a?=?3;?
2.?int?b?=?0;?
3.?int?c?=?a/b;?
Segment?2:?
4.?float?a?=?1.0F;?
5.?float?b?=?0.0F;?
6.?float?c?=?a/b;?
1)?When?executed,?both?segments?will?cause?an?exception?to?be?thrown.?
2)?When?executed,?neither?segment?will?cause?an?exception?to?be?thrown.?
3)?Only?Segment?1?will?throw?an?exception.?
4)?Only?Segment?2?will?throw?an?exception.?

Q152?Which?of?the?following?classes?override?the?equals()?method.?
1)?String?
2)?Integer?
3)?Double?
4)?Date?
5)?File?

Q153?Which?of?the?following?is?the?default?layout?manager?for?a?panel.?
1)?BorderLayout?
2)?FlowLayout?
3)?GridBagLayout?
4)?GridLayout?
5)?None?of?the?above.?

Q154?True?or?False.?
The?StringBuffer?class?inherits?from?the?String?class.?
1)?True?
2)?False?

Q155?True?or?False.?
The?class?String?has?a?concat()?method,?while?the?StringBuffer?class?has?an?append()?method.?
1)?True?
2)?False?

Q156?True?or?False.?
The?primative?wrapper?classes?Integer,?Double?and?Float?all?inherit?directly?from?the?java.lang.Wrapper?class.?
1)?True?
2)?False?

Q157?Which?of?the?following?are?valid?methods?for?the?Applet?class.?
1)?start()?
2)?stop()?
3)?init()?
4)?destroy()?
5)?kill()?

Q158?True?or?False.?
A?label?can?only?display?a?single?line?of?text.?
1)?True?
2)?False?

Q159?Which?of?the?following?are?valid?methods?for?the?Math?class.?
1)?random()?
2)?Random()?
3)?toDegrees()?
4)?square()?
5)?sqr()?

Q160?True?or?False.?
JDK?1.2?contains?an?Arrays?class?which?provides?various?methods?for?manipulating?arrays?(such?as?searching?and?sorting).?
1)?True?
2)?False?

Q161?True?or?False.?
The?Class?class?has?no?public?constructor.?
1)?True?
2)?False?

Q162?Which?of?the?following?statements?is?true?with?regard?to?persistence.?
1)?"Serializable"?is?a?keyword?within?the?Java?language.?
2)?"Serializable"?is?an?interface,?which?classes?can?implement.?
3)?"Serializable"?is?a?class,?which?other?classes?can?extend.?
4)?None?of?the?above.?

Q163?Which?of?the?following?statements?is?correct?with?regard?to?threads.?
1)?"Runnable"?is?a?keyword?within?the?Java?language,?used?to?identify?classes?which?can?exist?as?separate?threads.?
2)?"Runnable"?is?an?interface,?which?classes?can?implement?when?they?wish?to?execute?as?a?separate?thread.?
3)?"Runnable"?is?a?class,?which?classes?can?extend?when?they?wish?to?execute?as?a?separate?thread.?
4)?None?of?the?above.?
5)?java?does?not?support?threads.?

Q164?Select?the?statements?which?are?valid?from?the?list?below.?
1)?The?primative?data?type?"char"?is?16-bits?wide.?
2)?Unicode?uses?16-bits?to?represent?a?character.?
3)?Unicode?uses?32-bits?to?represent?a?character.?
4)?UTF?uses?24-bits?to?represent?a?character.?
5)?UTF?uses?as?many?bits?as?are?needed?to?represent?a?character.?

Q165?When?a?Frame?is?constructed,?it?has?no?size?and?is?not?displayed.?Which?of?the?following?methods?can?be?called?to?display?the?Frame.?
1)?setSize()?
2)?setBounds()?
3)?setDisplayable()?
4)?setVisible()?
5)?setState()?

Q166?Which?one?of?the?following?is?correct?(assume?A?and?B?are?correctly?defined).?
1)?if?(A?instanceOf?B)?
2)?if?(A?instanceof?B)?
3)?if?(A.instanceOf(B))?
4)?if?(A?instanceof(B))?

Q167?What?is?displayed?when?the?following?is?executed:?
double?d1?=?-0.5;?
System.out.println("Ceil?d1?=?"?+?Math.ceil(d1));?
System.out.println("floor?d1?=?"?+?Math.floor(d1));?
1)?Ceil?d1?=?-0.0?
floor?d1?=?-1.0?
2)?Ceil?d1?=?0.0?
floor?d1?=?-1.0?
3)?Ceil?d1?=?-0.0?
floor?d1?=?-0.0?
4)?Ceil?d1?=?0.0?
floor?d1?=?0.0?
5)?Ceil?d1?=?0?
floor?d1?=?-1?

Q168?Select?the?layour?manager?which?is?described?by?the?following:?
"It?arranges?its?constituent?components?in?horizontal?rows.?It?will?attempt?to?fit?as?many?components?as?possible?into?the?first?row,?and?remaining?components?will?spill?over?into?subsequent?rows.?Components?always?appear?left?to?right,?in?the?order?they?were?added?to?the?container."?
1)?FlowLayout?
2)?GridLayout?
3)?CardLayout?
4)?TransverseFlowLayout?
5)?GridBagLayout?

Q169?True?or?False?
The?argument?for?a?"case"?statement?must?be?a?constant?or?a?constant?expression?which?can?be?evaluated?at?compile?time.?
1)?True?
2)?False?

Q170?Select?the?valid?code?fragments?from?the?following?list:?
1)?public?transient?static?final?int?_FRAMEX?=?850;?
2)?this("a",?"b");?
[assuming?a?constructor?of?the?type?xxx(String,?String)?exists?for?this?class]?
3)?private?transient?static?final?int?_FRAMEX?=?850;?
4)?boolean?b?=?0;?

Q171?True?or?False.?
The?File?class?can?represent?either?a?file?or?a?directory?within?a?file?system.?
1)?True?
2)?False?

Q172?True?or?False.?
The?argument?for?a?while()?statement?MUST?be?a?boolean.?
1)?True?
2)?False?

Q173?True?or?False.?
The?right-hand?operand?of?the?instanceof?operator?can?be?an?interface;?eg?
a?instanceof?b?
where?b?is?an?interface.?
1)?True?
2)?False?

Q174?Consider?the?following?class:?
public?class?Test{?
public?int?secret;?
}?
Which?of?the?following?is?the?correct?way?to?make?the?variable?'secret'?read-only.?

1)?Declare?'secret'?to?be?private.?
2)?Declare?the?class?Test?to?be?private.?
3)?Declare?'secret'?to?be?private?and?write?a?method?getSecret()?which?returns?the?value?of?'secret'.?
4)?Declare?'secret'?to?be?transient.?
5)?Declare?'secret'?to?be?static.?

Q175?Which?one?of?the?following?methods?of?the?Math?class?can?be?used?to?find?the?square?root?of?a?number.?
1)?squareRoot()?
2)?sqrt()?
3)?root()?
4)?sqr()?
5)?None?of?the?above.?You?use?the?pow()?method.?

Q176?To?which?layout?manager?does?the?following?statement?refer:?
"it?preserves?the?preferred?size?(width?and?height)?of?each?component".?
1)?Flow?Layout?
2)?Border?Layout?
3)?Grid?Layout?
4)?Grid?Bag?Layout?
5)?None?of?the?above.?All?layout?managers?alter?the?dimensions?of?their?containing?components.?

Q177?Consider?the?following?code?fragment,?and?select?the?correct?statements(s):?
1.?public?class?Test?extends?MyBase?implements?MyInterface{?
2.?int?x?=?0;?
3.?
4.?public?Test(int?inVal)?throws?Exception{?
5.?if?(inVal?!=?this.x){?
6.?throw?new?Exception("Invalid?input");?
7.?}?
8.?}?
9.?
10.?public?static?void?main(String?args[]){?
11.?Test?t?=?new?Test(4);?
12.?}?
13.}?
1)?The?code?fails?to?compile?at?line?1.?It?is?not?valid?to?both?implement?an?interface?and?extend?from?a?parent?class?simultaneously.?
2)?The?code?fails?to?compile?at?line?4.?It?is?not?valid?for?constructors?to?throw?exceptions.?
3)?The?code?fails?to?compile?at?line?6,?because?this?is?not?valid?way?to?throw?an?exception.?
4)?The?code?fails?to?compile?at?line?11.?The?compiler?complains?that?there?is?an?uncaught?exception.?
5)?The?code?fails?to?compile?at?line?5,?because?this?is?not?a?valid?way?to?reference?variable?x.?

Q178?Consider?the?following?real-life?relationships,?and?select?the?code?fragment?which?most?closely?represents?it.?
An?employee?is?a?person.?An?employee?has?zero?or?more?dependants.?
?[for?the?code?fragments,?assume?that?all?relevant?packages?are?imported,?and?all?relevant?class?definitions?exist].?
1)?class?Employee?extends?Dependants{?
Person?p;?
}?
2)?class?Person?extends?Employee{?
Vector?dependants;?
}?
3)?class?Employee?extends?Person{?
Vector?dependants;?
}?
4)?abstract?class?Person?extends?Dependants{?
Employee?e;?
}?
5)?class?Dependant?implements?Employee{?
Vector?person;?
}?

Q179?Which?of?the?following?are?valid?declarations?for?a?native?method.?
1)?public?native?void?aMethod();?
2)?private?native?String?aMethod();?
3)?private?native?boolean?aMethod(int?val){};?
4)?public?native?int?aMethod(String?test);?
5)private?native?boolean?aMethod(boolean?flag,?Integer?val);?

Q180?Which?of?the?following?are?valid?ways?to?define?an?octal?literal?of?value?17?(octal).?
1)?private?final?int?theNumber?=?0x17;?
2)?private?final?int?theNumber?=?017;?
3)?public?int?theNumber?=?017;?
4)?public?int?theNumber?=?(octal)17;?
5?)public?int?THE_NUMBER?=?017;?

Q181?Consider?the?following?piece?of?code?and?select?all?statements?which?yield?a?boolean?value?of?true?as?a?result.?
Double?d1=new?Double(10.0);?
Double?d2=new?Double(10.0);?
int?x=10;?
float?f=10.0f;?
1)?d1?==?d2;?
2)?d1?==?x;?
3)?f?==?x;?
4)?d1.equals(d2);?
5)?None?of?the?above?

Q182?Given?the?following?definition:?
String?s?=?null;?
Which?code?fragment?will?cause?an?exception?of?type?NullPointerException?to?be?thrown.?
1)?if?((s?!=?null)?&?(s.length()>0))?
2)?if?((s?!=?null)?&&?(s.length()>0))?
3)?if?((s?!=?null)?|?(s.length()>0))?
4)?if?((s?!=?null)?||?(s.length()>0))?
5)?None?of?the?above.?

Q183?Which?of?the?following?are?valid?declarations?for?a?2x2?array?of?integers.?
1)?int?a[][]?=?new?int[10,10];?
2)?int?a[][]?=?new?int?[10][10];?
3)?int?a[10,10]?=?new?int?[10][10];?
4)?int?[][]a?=?new?int?[10][10];?
5)?int?[]a[]?=?new?int?[10][10];?

Q184?Which?values?of?variable?x?will?show?"Message?2".?
switch(x)?
{?
case?1?:?
System.out.println("Message?1");?
case?2?:?
case?3?:?
System.out.println("Message?2");?
default?:?
System.out.println("End");?
}?
1)?1?
2)?2?
3)?3?
4)?4?
5)?none?

Q185?What?is?the?result?of?the?following?code?:?
public?class?SuperEx?{?
String?r;?
String?s;?
public?SuperEx(String?a,String?b)?{?
r?=?a;?

s?=?b;?
}?
public?void?aMethod()?{?
System.out.println("r?:"?+?r);?
}?
}?
public?class?NewSuper?extends?SuperEx?{?
public?NewSuper(String?a,String?b)?{?
super(a,b);?
}?
public?static?void?main(String?args?[])?{?
SuperEx?a?=?new?SuperEx("Hi","Tom");?
SuperEx?b?=?new?NewSuper("Hi","Bart");?
a.aMethod();?
b.aMethod();?
}?
public?void?aMethod()?{?
System.out.println("r?:"?+?r?+?"?s:"?+?s);?
}?
}?
1)?The?following?is?displayed:?
r:Hi?
s:Hi?
2)?Compiler?error?at?the?line?"SuperEx?b?=?new?NewSuper("Hi","Bart");"?
3)?The?following?is?displayed:?
r:Hi?
r:Hi?s:Bart?
4)?The?following?is?displayed?
r:Hi?s:Tom?
r:Hi?s:Bart?

Q186?You?have?a?class?with?a?certain?variable?and?you?don't?want?that?variable?to?be?accessible?to?ANY?other?class?but?your?own.?Your?class?must?be?sub-classable.?
Which?keyword?do?you?add?to?the?variable.?
1)?private?
2)?public?
3)?transient?
4)?final?
5)?abstract?

Q187?You?get?this?description?of?a?class?:?
Employee?is?a?person.?For?every?employee,?we?keep?a?vector?with?the?working?hours,?an?integer?for?the?salary?and?a?variable?that?can?be?true?or?false?whether?or?not?the?employee?has?a?company?car.?
Indicate?which?of?the?following?would?be?used?to?define?the?class?members.?
1)?Vector?
2)?Employee?
3)?Object?
4)?boolean?
5)?int?

Q188?Which?line?of?code?can?be?inserted?in?place?of?the?comments,?to?perform?the?initialisation?described?by?the?comments:?
public?class?T?{?
int?r;?
int?s;?
T(int?x,?int?y)?{?
r?=?x;?
s?=?y;?
}?
}?
class?S?extends?T?{?
int?t;?
public?S(int?x,?int?y,?int?z){?
//?insert?here?the?code?
//?that?would?do?the?correct?initialisation?
//?r=?x?and?s=?y?
t=z;?
}?
}?
1)?T(x,?y);?
2)?this(x,?y);?
3)?super(x,?y);?
4)?super(x,?y,?z);?
5)?None?

Q189?Suppose?a?MyException?should?be?thrown?if?Condition()?is?true,?which?statements?do?you?have?to?insert???
1:?public?aMethod?{?
2:?
3:?if?(Condition)?{?
4:?
5:?}?
6:?
7:?}?
1)?throw?new?Exception()?at?line?4?
2)?throw?new?MyException()?at?line?4?
3)?throw?new?MyException()?at?line?6?
4)?throws?new?Exception()?at?line?2?
5)?throws?MyException?at?line?1?

Q190?Suppose?a?NullPointerException?is?thrown?by?test().?Which?message?is?displayed??
void?Method(){?
try?{?
test();?
System.out.println("Message1");?
}?
catch?(ArrayOutOfBoundsException?e)?{?
System.out.println("Message2");?
}?
finally?{?
System.out.println("Message3");?
}?
System.out.println("Message4");?
}?
1)?Message1?
2)?Message2?
3)?Message3?
4)?Message4?
5)?None?of?the?above.?

Q191?Choose?the?class?that?can?hold?multiple?equal?objects?in?an?ordered?way.?
1)?Map?
2)?Collection?
3)?List?
4)?Set?
5)?Vector?

Q192?Consider?the?following?variables?definitions.?
Float?f1?=?new?Float("10F");?
Float?f2?=?new?Float("10F");?
Double?d1?=?new?Double("10D");?
Which?of?the?following?yields?a?boolean?value?of?true.?
1)?f1?==?f2?
2)?f1.equals(f2)?
3)?f2.equals(d1)?
4)?f2.equals(new?Float("10"))?

Q193?What?does?the?getID()?method?of?AWTEvent?tell?us.?
1)?Tells?us?the?x?and?y?coords?of?the?mouse?at?the?event?time.?
2)?Tells?us?which?Object?the?event?originated?from.?

3)?Tells?us?which?special?keys?were?pressed?at?the?event?time.?
4)?Tells?us?the?event?type.?
5)?Tells?us?the?how?many?pixels?were?between?the?mouse?pointer?and?text?on?a?Canvas.?

Q194?What?is?the?return?type?of?an?Eventlistener???
1)?int?
2)?NULL?
3)?void?
4)?boolean?
5)?Object?

Q195?You?create?a?Long?object?using?the?following:?
Long?val?=?new?Long("11");?
Which?of?the?following?will?return?the?value?of?the?object?as?a?byte?value??
1)?byte?b?=?(byte)val;?
2)?byte?b?=?val.getByte();?
3)?byte?b?=?(byte)val.getValue();?
4)?byte?b?=?val.byteValue();?
5)?None?of?the?above.?

Q196?Consider?the?following.?
String?s1?=?"abc";?
String?s2?=?"def";?
String?s3?=?new?String(s2);?
s2?=?s1;?
What?is?the?value?of?s3?after?the?final?line?of?code?is?executed??
1)?"abc"?
2)?"def"?
3)?null?
4)?An?exception?is?thrown?when?"s2?=?s1"?is?executed.?

Q197?What?tags?are?mandatory?when?creating?HTML?to?display?an?applet?
1)?name,?width,?height?
2)?code,?name?
3)?codebase,?height,?width?
4)?code,?width,?height?
5)?None?of?the?above?

Q198?What?is?displayed?when?the?following?code?is?executed:?
String?s1?=?"?hello?world?";?
String?s2?=?s1.trim();?
System.out.println(s2);?
1)?"?hello?world"?
2)?"hello?world?"?
3)?"hello?world"?
4)?"?hello?world?"?
5)?"helloworld"?

Q199?Which?of?the?following?are?methods?within?the?String?class.?
1)?substring()?
2)?startsWith()?
3)?toString()?
4)?toUpperCase()?
5)?indexOf()?

Q200?True?or?False.?
APPLET?tags?must?appear?between?BODY?and?/BODY?tags.?
1)?True?
2)?False?

ANSWER:?
1.?1,2?
Answers?3,?4?and?5?are?incorrect?because?these?operations?requires?that?an?int?(c)?be?converted?to?a?boolean,?or?the?boolean?be?converted?to?an?int.?Both?of?these?conversions?are?illegal.?
2.?5?
A?constructor?cannot?be?abstract,?final,?native,?static?or?synchronized.?Refer?to?the?Java?Language?Specification?(section?8.6.3,?version?1.0).?
3.?4?
In?general,?all?components?are?resized?and?only?retain?their?preferred?height?in?the?NORTH?region.?However,?the?CheckBox?is?not?deformable,?so?it?retains?it's?preferred?size.?
4.?1,3,4?
5.?1?
6.?3?
When?a?File?class?is?constructed,?it?simply?creates?a?handle?to?a?File?object.?No?files?are?created?on?the?local?harddisk.?
As?the?JDK?API?documentation?points?out,?the?File?class?is?"an?abstract?representation?of?file?and?directory?pathnames".?
The?File?class?also?contains?directory?separator?attributes,?which?are?platform?specific.?Therefore,?the?directory?separator?used?is?irrelevant.?

Also,?since?the?File?class?simply?creates?a?reference?to?a?file?object,?no?exception?is?thrown?if?the?file?already?exists?on?the?disk.?
7.?1,4,5?
Answer?1?is?correct,?because?in?read?mode,?the?file?must?exist?if?any?other?operations?are?to?be?performed?on?it.?
The?RandomAccessFile?is?not?compatible?with?the?Stream?or?reader/writer?classes,?so?Answer?3?is?incorrect.?
8.?3?
Strings?are?immutable,?and?so?they?cannot?be?modified.?However,?as?the?JDK?API?documentation?will?show,?the?String?class?has?a?replace()?method,?so?answer?1?is?incorrect.?
If?line?2?read?as?"s?=?s.replace('d',?'q')"?then?a?new?object?would?be?created?and?assigned?to?s.?The?value?of?this?new?String?object?would?be?"abcqefgh".?However,?as?line?2?is?presented,?no?new?object?is?created,?and?so?'s'?remains?unchanged.?
9.?1,5?
10.?2?
I?came?across?the?statement?during?my?study?for?the?exam,?and?simply?noted?it?as?fact.?I?never?really?looked?too?deeply?into?it?-?so?please?don't?email?me?for?an?explanation?:-)?
11.?1,4,5?

Therefore,?Answer?1?is?correct,?because?class?B?attempts?to?override?method()?to?be?less?public?(ie,?protected?to?"friendly").?

Answer?2?is?incorrect,?because?a?protected?variable?or?method?is?always?available?to?child?classes?(this?is?the?purpose?of?the?protected?keyword).?

Answer?3?is?incorrect,?because?all?the?information?needed?to?verify?this?code?is?available?at?compile?time.?

Answers?4?and?5?are?correct?because?adding?either?"public"?or?"protected"?to?line?7?actually?moves?it?higher?up?the?access?hierarchy?(ie,?more?public?than?friendly).?

12.?1?
13.?2?
14.?1?
15.?3?
16.?2?
The?rule?for?accessing?methods?and?variables?in?a?class?hierarchy?is?as?follows:?

-the?object?reference?is?used?when?accessing?variables?(so?the?value?of?b.x?is?therefore?2).?

-the?underlying?object?is?used?when?accessing?methods?(so?the?method?called?is?actually?the?method?defined?in?Subclass,?and?in?Subclass,?x?=3).?
17.?1?
18.?2?
19.?2?
20.?1,2,3?
1.?3?
22.?1?
23.?1?
24.?1?
25.?4?
26.?1,4,5?
Answer?1?is?correct,?because?x?is?declared?as?private?to?class?A?and?is?therefore?not?available?to?any?other?class?(even?subclasses).?
Answer?3?is?totally?meaningless,?but?sounds?vaguely?plausible!?
Answer?4?is?correct,?because?the?only?problem?with?the?code?is?the?attempt?to?reference?the?variable?x.?
Answer?5?is?correct?(see?answer?4).?
27.?3?
28.?2,3,4,5?
29.?1?
Answer?2?is?incorrect,?since?the?{}?defines?an?empty?method?(but?still?a?method)?so?it?is?not?abstract.?
Abstract?methods?cannot?be?static,?so?answer?3?is?incorrect.?
Abstract?and?final?are?almost?opposite?in?meaning?and?therefore?do?not?form?a?valid?keyword?combination?(final?means?a?method?can't?be?overridden,?abstract?means?a?method?must?be?overridden),?so?answer?4?is?incorrect.?
30.?2?
31.?4?
Interfaces?cannot?have?constructors,?only?classes?have?constructors.?
Answer?2?is?a?valid?statement?when?dealing?with?classes,?but?not?in?the?context?of?the?code?in?the?question.?
Answer?5?is?totally?untrue,?but?potentially?confusing?:-)?
32.?1?
33.?1,2,4?
34.?1?
Answer?2?is?incorrect,?because?booleans?can't?have?integer?values?(in?this?case,?"1").?
Answer?3?is?an?meaningless?statement.?
Answer?5?is?incorrect,?attempting?to?confuse?C/C++?and?Java?ways?of?defining?true?and?false?boolean?values.?
35.?2,4?
36.?2?
37.?2?
38.?1,2?
39.?3?
40.?1?
41.?2?
42.?3?
43.?1,3?
44.?1,2,3?
45.?2?
46.?1,2,4,5?
47.?1?
48.?2?
49.?1.4?
50.?3,4?
Answer?1?is?incorrect,?because?a?class?can?have?final?methods?and?variables?without?the?need?for?the?entire?class?to?be?final.?
Answer?2?is?incorrect,?because?the?type?of?error?in?this?code?is?detectable?at?compile?time.?
Answer?5?is?invalid.?Final?can?be?applied?to?primitives.?
51.?4?
52.?1?
53.?1,2,3,4,5?
54.?2?
55.?2.3?
56.?3?
57.?1,3,4?
58.?3,5?
59.?1,3,4,5?
60.?5?
61.?3?
62.?4?
63.?1,4?
64.?4?
65.?2,3?
66.?1,3,4,5?
67.?5?
68.?2?
69.?4?
70.?5?
71.?4?
72.?2?
73.?3?
74.?2?
75.?1?
76.?1?
77.?4?
78.?3?
79.?2?
80.?3?
81.?3?
82.?3?
83.?1,2,5?
84.?5?
85.?4?
86.?2,3?
There?are?several?things?wrong?with?this?code:?
-?class?A?must?be?declared?as?abstract,?since?method()?is?declared?as?abstract?
-?if?class?A?is?declared?as?abstract,?then?the?code?will?compile?correctly?
-?if?the?abstract?declaration?of?method()?in?class?A?is?removed,?the?code?will?compile?(however,?the?entire?line?2?must?now?read?as?follows:?
int?method(){}?
In?other?words,?a?method?body?must?now?be?supplied?since?the?method?is?no?longer?abstract.?
87.?3?
88.?2,5?
89.?3?
90.?2?
91.?1?
92.?3,4,5?
93.?2,3,5?
94.?1,5?
95.?2,3?
96.?3.?
97.?1,2?
98.?2?
The?instanceof?operator?can?be?used?as?follows:?
-?on?classes?to?see?if?a?particular?class?is?derived?from?another?(ie,?is?an?instance?of)?
-?on?interfaces?to?see?if?a?class?implements?a?particular?interface?
99.?1,3,4?
100.?1,2,3,4,5?
101.?1,2,3,4,5?
102.?2,3,4?
103.?2?
104.?1,2,5?
105.?4?
106.?3,4,5?
107.?4,5?
108.?3?
109.?1,3,5?
110.?3?
111.?1?
112.?4?
113.?1?
114.?4?
115.?2?
1?will?not?compile,?because?123?defaults?to?type?int,?and?there?is?no?constructor?of?the?Byte?class?which?takes?type?int?as?a?parameter.?
2?compiles?correctly,?because?a?parseable?string?is?a?valid?parameter?for?the?Byte?constructor.?
3?fails?to?compile,?because?there?is?no?no-args?constructor?for?the?Byte?class.?
4?fails?to?compile.?While?the?cast?to?an?int?is?valid,?the?same?reasons?as?Answer?1?apply.?
5?fails?to?compile,?because?the?value?0x123?is?a?hex?value,?and?equates?to?a?decimal?value?of?291.?This?is?not?within?the?valid?range?for?the?Byte?value.?
116.?2?
117.?2,4?
118.?1,5?
119.?2?
120.?2,3?
121.?1,2?
122.?1?
123.?2?
124.?2,4?
125.?3,4,5?
126.?1,2,3?
127.?1?
Thanks?to?Prasad?for?rightly?pointing?out?that?Answer?2?above?also?works?for?a?container?which?uses?the?Flow?Layout?manager?(even?though?it?doesn't?have?a?"Center"?area").?
This?can?be?explained?by?the?fact?that?a?container?such?as?a?Panel?inherits?from?java.awt.Container,?which?has?a?method?with?a?signature?as?follows:?
add(String,?Component)?
However,?while?this?is?symantically?correct?(ie,?it?will?compile?and?function?correctly),?it?can't?be?considered?as?a?valid?answer?since?Flow?layout?doesn't?have?the?concept?of?a?"Center"?area?-?at?least,?that's?my?opinion?:-)?
However,?this?raises?an?interesting?point?-?where?possible,?you?should?use?static?class?variables,?where?a?choice?is?available?-?eg,?use?BorderLayout.NORTH?instead?of?"NORTH"?when?adding?components?to?a?container.?This?will?ensure?that?any?errors?are?trapped?at?compile?time,?rather?than?at?run-time?:-)?
128.?2?
129.?3?
130.?3?
131.?5?
132.?1?
133.?3?
134.?3?
135.?1,2,4,5?
136.?4,5?
137.?1?
138.?1?
139.?1?
140.?1?
141.?3?
142.?1,2?
143.?3?
144.?5?
145.?1,2,3,4?
146.?1,2,3?
147.?4?
148.?1?
149.?2?
150.?1?
151.?3?
152.?1,2,3,4,5?
153.?2?
154.?2?
155.?1?
156.?2?
157.?1,2,3,4?
158.?1?
159.?1,3?
160.?1?
161.?1?
162.?2?
163.?2?
164.?1,2,5?
165.?1,2,4?
166.?2?
167.?1?
168.?1?
169.?1?
170.?1,2,3?
171.?1?
172.?1?
173.?1?
174.?3?
175.?2?
176.?1?
177.?4?
178.?3?
179.?1,2,4,5?
180.?2,3,5?
181.?3,4?
182.?1,3,4?
183.?2,4,5?
184.?1,2,3?
185.?3?
186.?1?
187.?1?
188.?3?
189.?2,5?
190.?3?
191.?5?
192.?2,4?
193.?4?
194.?3?
195.?4?
196.?2?
197.?4?
198.?3?
199.?1,2,3,4,5?
200.?1

SCJP?模擬考試題,?筆試常考

http://beansoft.java-cn.org/download/scjp_emulator.zip?700KB?Java?1.4?版本

?

是我很早以前買的一本英文?SCJP?輔導(dǎo)書里面所附帶的代碼.
下載后解壓縮得到幾個(gè)?JAR?文件?下載后?Windows?下可以雙擊運(yùn)行,?點(diǎn)擊最大化后,?然后點(diǎn)擊?Mark?按鈕就可以看到正確答案和解釋了.
Linux/Windows?下都通過命令行鍵入
java?-jar?Final.jar?這樣的命令即可運(yùn)行.?

現(xiàn)在的?Java?筆試題?的基礎(chǔ)部分(core?java)很多都是從類似這樣的英文題里面抽取出來的,?基本上熟悉之后筆試題會(huì)答的很漂亮.
界面截圖:?

再轉(zhuǎn)載:??閱讀完此貼你才可以大膽的高薪工作！http://bbs.tarena.com.cn/topic.cgi?forum=1&topic=10848&show=0
?大家找工作就要面試，有面試就有對(duì)付面試的辦法。以下一些題目來自我朋友痛苦的面試經(jīng)歷，他給我總結(jié)了一下，我拿來和大家分享！提這些問題的公司包括IBM,?E*Trade,?Siebel,?Motorola,?SUN,?以及其它大小公司。?　　
???面試是沒什么道理可講的，它的題目有的不合情理、脫離實(shí)際。有在紙上寫的，有當(dāng)面考你的，也有在電話里問的，給你IDE的估計(jì)很少(否則你趕快去買彩票，?說不定中)。所以如果你看完此文后，請(qǐng)不要抱怨說這些問題都能用IDE來解決。你必須在任何情況下準(zhǔn)確回答這些問題，在面試中如果出現(xiàn)一兩題回答不準(zhǔn)確很有可能你就被拒之門外了。?　　當(dāng)然這些都是Java的基本題，那些面試的人大多數(shù)不會(huì)問你Hibernate有多先進(jìn)，Eclipse的三個(gè)組成部分，或command?design?pattern，他們都是老一輩了，最喜歡問的就是基礎(chǔ)知識(shí)。別小看了這些基礎(chǔ)，我朋友水平挺可以的，結(jié)果就栽在一道基礎(chǔ)知識(shí)的問題上，和高薪無緣。???
???希望這些知識(shí)點(diǎn)對(duì)大家有所幫助,愿大家從達(dá)內(nèi)出來后都能找到高薪的工作！

第一，談?wù)刦inal,?finally,?finalize的區(qū)別。?　　final?用于聲明屬性，方法和類，分別表示屬性不可變，方法不可覆蓋，類不可繼承。finally是異常處理語句結(jié)構(gòu)的一部分，表示總是執(zhí)行。finalize是Object類的一個(gè)方法，在垃圾收集器執(zhí)行的時(shí)候會(huì)調(diào)用被回收對(duì)象的此方法，可以覆蓋此方法提供垃圾收集時(shí)的其他資源回收，例如關(guān)閉文件等。　　

第二，Anonymous?Inner?Class?(匿名內(nèi)部類)?是否可以extends(繼承)其它類，是否可以implements(實(shí)現(xiàn))interface(接口)??可以繼承其他類或完成其他接口，在swing編程中常用此方式。　　

第三，Static?Nested?Class?和?Inner?Class的不同，說得越多越好(面試題有的很籠統(tǒng))。?Static?Nested?Class是被聲明為靜態(tài)（static）的內(nèi)部類，它可以不依賴于外部類實(shí)例被實(shí)例化。而通常的內(nèi)部類需要在外部類實(shí)例化后才能實(shí)例化。　　

第四，&和&&的區(qū)別。?&是位運(yùn)算符，表示按位與運(yùn)算，&&是邏輯運(yùn)算符，表示邏輯與（and）.　　

第五，HashMap和Hashtable的區(qū)別。?HashMap是Hashtable的輕量級(jí)實(shí)現(xiàn)（非線程安全的實(shí)現(xiàn)），他們都完成了Map接口，主要區(qū)別在于HashMap允許空（null）鍵值（key）,由于非線程安全，效率上可能高于Hashtable.　　

第六，Collection?和?Collections的區(qū)別。?　　Collection是集合類的上級(jí)接口，繼承與他的接口主要有Set?和List.Collections是針對(duì)集合類的一個(gè)幫助類，他提供一系列靜態(tài)方法實(shí)現(xiàn)對(duì)各種集合的搜索、排序、線程安全化等操作。　　

第七，什么時(shí)候用assert。?1.4新增關(guān)鍵字（語法），用于測(cè)試boolean表達(dá)式狀態(tài)，可用于調(diào)試程序。使用方法?assert?<boolean表達(dá)式>，表示如果表達(dá)式為真（true）,則下面的語句執(zhí)行，否則拋出AssertionError。另外的使用方式assert?<?boolean表達(dá)式>:<other表達(dá)式>，表示如果表達(dá)式為真，后面的表達(dá)式忽略，否則后面表達(dá)式的值用于AssertionError的構(gòu)建參數(shù)。注意編譯時(shí)要增加-source?1.4?參數(shù)，否則報(bào)錯(cuò)。]運(yùn)行時(shí)要增加?-ea參數(shù)，否則assert行被忽略　　

第八，GC是什么??為什么要有GC??　　GC是垃圾收集的意思（Gabage?Collection）,內(nèi)存處理是編程人員容易出現(xiàn)問題的地方，忘記或者錯(cuò)誤的內(nèi)存回收會(huì)導(dǎo)致程序或系統(tǒng)的不穩(wěn)定甚至崩潰，Java提供的GC功能可以自動(dòng)監(jiān)測(cè)對(duì)象是否超過作用域從而達(dá)到自動(dòng)回收內(nèi)存的目的，Java語言沒有提供釋放已分配內(nèi)存的顯示操作方法。?　　

第九，String?s?=?new?String("xyz");創(chuàng)建了幾個(gè)String?Object??兩個(gè)　　

第十，Math.round(11.5)等於多少??Math.round(-11.5)等於多少??Math.round(11.5)==12Math.round(-11.5)==-11round方法返回與參數(shù)最接近的長(zhǎng)整數(shù)，參數(shù)加1/2后求其floor.　　

第十一，short?s1?=?1;?s1?=?s1???1;有什么錯(cuò)??short?s1?=?1;?s1??=?1;有什么錯(cuò)??short?s1?=?1;?s1?=?s1???1;?（s1?1運(yùn)算結(jié)果是int型，需要強(qiáng)制轉(zhuǎn)換類型）short?s1?=?1;?s1??=?1;（可以正確編譯）　　

第十二，sleep()?和?wait()?有什么區(qū)別??sleep是線程類（Thread）的方法，導(dǎo)致此線程暫停執(zhí)行指定時(shí)間，給執(zhí)行機(jī)會(huì)給其他線程，但是監(jiān)控狀態(tài)依然保持，到時(shí)后會(huì)自動(dòng)恢復(fù)。調(diào)用sleep不會(huì)釋放對(duì)象鎖。wait是Object類的方法，對(duì)此對(duì)象調(diào)用wait方法導(dǎo)致本線程放棄對(duì)象鎖，進(jìn)入等待此對(duì)象的等待鎖定池，只有針對(duì)此對(duì)象發(fā)出notify方法（或notifyAll）后本線程才進(jìn)入對(duì)象鎖定池準(zhǔn)備獲得對(duì)象鎖進(jìn)入運(yùn)行狀態(tài)。　　

第十三，Java有沒有g(shù)oto??沒有　　很十三的問題，如果哪個(gè)面試的問到這個(gè)問題，我勸你還是別進(jìn)這家公司。（完）（job.sohu.com）

第十四，數(shù)組有沒有l(wèi)ength()這個(gè)方法??String有沒有l(wèi)ength()這個(gè)方法？數(shù)組沒有l(wèi)ength()這個(gè)方法，有l(wèi)ength的屬性。String有有l(wèi)ength()這個(gè)方法。

第十五，Overload和Override的區(qū)別。Overloaded的方法是否可以改變返回值的類型?方法的重寫Overriding和重載Overloading是Java多態(tài)性的不同表現(xiàn)。重寫Overriding是父類與子類之間多態(tài)性的一種表現(xiàn)，重載Overloading是一個(gè)類中多態(tài)性的一種表現(xiàn)。如果在子類中定義某方法與其父類有相同的名稱和參數(shù)，我們說該方法被重寫?(Overriding)。子類的對(duì)象使用這個(gè)方法時(shí)，將調(diào)用子類中的定義，對(duì)它而言，父類中的定義如同被"屏蔽"了。如果在一個(gè)類中定義了多個(gè)同名的方法，它們或有不同的參數(shù)個(gè)數(shù)或有不同的參數(shù)類型，則稱為方法的重載(Overloading)。Overloaded的方法是可以改變返回值的類型。

第十六，Set里的元素是不能重復(fù)的，那么用什么方法來區(qū)分重復(fù)與否呢??是用==還是equals()??它們有何區(qū)別?Set里的元素是不能重復(fù)的，那么用iterator()方法來區(qū)分重復(fù)與否。equals()是判讀兩個(gè)Set是否相等。equals()和==方法決定引用值是否指向同一對(duì)象equals()在類中被覆蓋，為的是當(dāng)兩個(gè)分離的對(duì)象的內(nèi)容和類型相配的話，返回真值。

第十七，給我一個(gè)你最常見到的runtime?exception。ArithmeticException,?ArrayStoreException,?BufferOverflowException,?BufferUnderflowException,?CannotRedoException,?CannotUndoException,?ClassCastException,?CMMException,?ConcurrentModificationException,?DOMException,?EmptyStackException,?IllegalArgumentException,?IllegalMonitorStateException,?IllegalPathStateException,?IllegalStateException,?ImagingOpException,?IndexOutOfBoundsException,?MissingResourceException,?NegativeArraySizeException,?NoSuchElementException,?NullPointerException,?ProfileDataException,?ProviderException,?RasterformatException,?SecurityException,?SystemException,?UndeclaredThrowableException,?UnmodifiableSetException,?UnsupportedOperationException

第十八，error和exception有什么區(qū)別?error?表示恢復(fù)不是不可能但很困難的情況下的一種嚴(yán)重問題。比如說內(nèi)存溢出。不可能指望程序能處理這樣的情況。exception?表示一種設(shè)計(jì)或?qū)崿F(xiàn)問題。也就是說，它表示如果程序運(yùn)行正常，從不會(huì)發(fā)生的情況。

第十九，List,?Set,?Map是否繼承自Collection接口?List，Set是Map不是

第二十，abstract?class和interface有什么區(qū)別?聲明方法的存在而不去實(shí)現(xiàn)它的類被叫做抽象類（abstract?class），它用于要?jiǎng)?chuàng)建一個(gè)體現(xiàn)某些基本行為的類，并為該類聲明方法，但不能在該類中實(shí)現(xiàn)該類的情況。不能創(chuàng)建abstract?類的實(shí)例。然而可以創(chuàng)建一個(gè)變量，其類型是一個(gè)抽象類，并讓它指向具體子類的一個(gè)實(shí)例。不能有抽象構(gòu)造函數(shù)或抽象靜態(tài)方法。Abstract?類的子類為它們父類中的所有抽象方法提供實(shí)現(xiàn)，否則它們也是抽象類為。取而代之，在子類中實(shí)現(xiàn)該方法。知道其行為的其它類可以在類中實(shí)現(xiàn)這些方法。接口（interface）是抽象類的變體。在接口中，所有方法都是抽象的。多繼承性可通過實(shí)現(xiàn)這樣的接口而獲得。接口中的所有方法都是抽象的，沒有一個(gè)有程序體。接口只可以定義static?final成員變量。接口的實(shí)現(xiàn)與子類相似，除了該實(shí)現(xiàn)類不能從接口定義中繼承行為。當(dāng)類實(shí)現(xiàn)特殊接口時(shí)，它定義（即將程序體給予）所有這種接口的方法。然后，它可以在實(shí)現(xiàn)了該接口的類的任何對(duì)象上調(diào)用接口的方法。由于有抽象類，它允許使用接口名作為引用變量的類型。通常的動(dòng)態(tài)聯(lián)編將生效。引用可以轉(zhuǎn)換到接口類型或從接口類型轉(zhuǎn)換，instanceof?運(yùn)算符可以用來決定某對(duì)象的類是否實(shí)現(xiàn)了接口。

第二十一，abstract的method是否可同時(shí)是static,是否可同時(shí)是native，是否可同時(shí)是synchronized?都不能

第二十二，接口是否可繼承接口??抽象類是否可實(shí)現(xiàn)(implements)接口??抽象類是否可繼承實(shí)體類(concrete?class)?接口可以繼承接口。抽象類可以實(shí)現(xiàn)(implements)接口，抽象類是否可繼承實(shí)體類，但前提是實(shí)體類必須有明確的構(gòu)造函數(shù)。

第二十三，啟動(dòng)一個(gè)線程是用run()還是start()?啟動(dòng)一個(gè)線程是調(diào)用start()方法，使線程所代表的虛擬處理機(jī)處于可運(yùn)行狀態(tài)，這意味著它可以由JVM調(diào)度并執(zhí)行。這并不意味著線程就會(huì)立即運(yùn)行。run()方法可以產(chǎn)生必須退出的標(biāo)志來停止一個(gè)線程。

第二十四，構(gòu)造器Constructor是否可被override?構(gòu)造器Constructor不能被繼承，因此不能重寫Overriding，但可以被重載Overloading。

第二十五，是否可以繼承String類?String類是final類故不可以繼承。

第二十六，當(dāng)一個(gè)線程進(jìn)入一個(gè)對(duì)象的一個(gè)synchronized方法后，其它線程是否可進(jìn)入此對(duì)象的其它方法?不能，一個(gè)對(duì)象的一個(gè)synchronized方法只能由一個(gè)線程訪問。

第二十七，try?{}里有一個(gè)return語句，那么緊跟在這個(gè)try后的finally?{}里的code會(huì)不會(huì)被執(zhí)行，什么時(shí)候被執(zhí)行，在return前還是后?會(huì)執(zhí)行，在return前執(zhí)行。

第二十八，編程題:?用最有效率的方法算出2乘以8等於幾?有C背景的程序員特別喜歡問這種問題。2?<<?3

第二十九，兩個(gè)對(duì)象值相同(x.equals(y)?==?true)，但卻可有不同的hash?code，這句話對(duì)不對(duì)?不對(duì)，有相同的hash?code。

第三十，當(dāng)一個(gè)對(duì)象被當(dāng)作參數(shù)傳遞到一個(gè)方法后，此方法可改變這個(gè)對(duì)象的屬性，并可返回變化后的結(jié)果，那么這里到底是值傳遞還是引用傳遞??是值傳遞。Java?編程語言只由值傳遞參數(shù)。當(dāng)一個(gè)對(duì)象實(shí)例作為一個(gè)參數(shù)被傳遞到方法中時(shí)，參數(shù)的值就是對(duì)該對(duì)象的引用。對(duì)象的內(nèi)容可以在被調(diào)用的方法中改變，但對(duì)象的引用是永遠(yuǎn)不會(huì)改變的。

第三十一，swtich是否能作用在byte上，是否能作用在long上，是否能作用在String上?switch（expr1）中，expr1是一個(gè)整數(shù)表達(dá)式。因此傳遞給?switch?和?case?語句的參數(shù)應(yīng)該是?int、?short、?char?或者?byte。long,string?都不能作用于swtich。

第三十二，編程題:?寫一個(gè)Singleton出來。Singleton模式主要作用是保證在Java應(yīng)用程序中，一個(gè)類Class只有一個(gè)實(shí)例存在。一般Singleton模式通常有幾種種形式:第一種形式:?定義一個(gè)類，它的構(gòu)造函數(shù)為private的，它有一個(gè)static的private的該類變量，在類初始化時(shí)實(shí)例話，通過一個(gè)public的getInstance方法獲取對(duì)它的引用,繼而調(diào)用其中的方法。public?class?Singleton?{　　private?Singleton(){}　　//在自己內(nèi)部定義自己一個(gè)實(shí)例，是不是很奇怪？　　//注意這是private?只供內(nèi)部調(diào)用　　private?static?Singleton?instance?=?new?Singleton();　　//這里提供了一個(gè)供外部訪問本class的靜態(tài)方法，可以直接訪問　　　　public?static?Singleton?getInstance()?{　　　　return?instance;?　　　　?}?}?第二種形式:?public?class?Singleton?{?　　private?static?Singleton?instance?=?null;　　public?static?synchronized?Singleton?getInstance()?{　　//這個(gè)方法比上面有所改進(jìn)，不用每次都進(jìn)行生成對(duì)象，只是第一次　　　?　　　//使用時(shí)生成實(shí)例，提高了效率！　　if?(instance==null)　　　　instance＝new?Singleton();return?instance;?　　}?}?其他形式:定義一個(gè)類，它的構(gòu)造函數(shù)為private的，所有方法為static的。
一般認(rèn)為第一種形式要更加安全些

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