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编码练习——Java-1-基础

發布時間：2025/3/21 java 14 豆豆

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基礎練習

輸出

public class MyApp {public static void main(String[] args) {System.out.println("我能學好Java語言！");} }

整數類型

public class Test {public static void main(String[] args) {byte mybyte = 124;short myshort = 32564;int myint = 45784612;long mylong = 46789451L;long result = mybyte+myshort+myint+mylong;System.out.println("四種類型相加的結果為："+result);} }

浮點型

public class Test {public static void main(String[] args) {float f1 = 12.23f;double d1 = 4562.12d;double d2 = 45678.1564;double result = f1+d1+d2;System.out.println("浮點數相加達到結果為："+result);} }

字符型

public class Test {public static void main(String[] args) {int i = 'd';char c = 97;System.out.println("字符d的Unicode碼是："+i);System.out.println("Unicode碼97代表的字符是："+c);} }

轉義字符

public class Test {public static void main(String[] args) {char char1 = '\\';char char2 = '\u2605';System.out.println("輸出反斜杠：" + char1);System.out.println("輸出五角星：" + char2);} }

變量（聲明與定義）

public class Test {public static void main(String[] args) {int i= 10;System.out.println("i的初值是："+i);i= 100;System.out.println("i現在的值是："+i);} }

聲明常量?
- final
- 一般大寫

public class Test {public static void main(String[] args) {final double PI = 3.1415926F; // final 大寫final boolean BOOL = true;} }

變量和常量（靜態變量）

public class Test {static final double PI = 3.14;static int age = 23;public static void main(String[] args) {final int number;number = 1235;age = 22;System.out.println("常量PI的值為："+PI);System.out.println("賦值后number的值為："+number);System.out.println("int型變量age的值為：" + age);} }

成員變量（靜態變量）和局部變量

public class Test {static int times = 3;public static void main(String[] args) {int times = 4;System.out.println("times的值為：" + times);System.out.println("times的值為：" + Test.times);} }

賦值運算符

public class Test {public static void main(String[] args) {int a,b,c;a = 15;c = b = a+4;System.out.println("c的值為：" + c);System.out.println("b的值為：" + b);} }

算術運算符

public static void main(String[] args) {float number1 = 45.56f;int number2 = 152;System.out.println("45.56f和152的和為：" + (number1+number2));System.out.println("45.56f和152的差為：" + (number1-number2));System.out.println("45.56f和152的積為：" + (number1*number2));System.out.println("45.56f和152的商為：" + (number1/number2));} }

關系運算符

public class Test {public static void main(String[] args) {int number1 = 4;int number2 = 5;System.out.println("4>5是否成立：" + (number1>number2));System.out.println("4<5是否成立：" + (number1<number2));System.out.println("4==5是否成立：" + (number1==number2));System.out.println("4!=5是否成立：" + (number1!=number2));System.out.println("4>=5是否成立：" + (number1>=number2));System.out.println("4<=5是否成立：" + (number1<=number2));} }

邏輯運算符

public class Test {public static void main(String[] args) {int a = 2;int b = 5;boolean result1 = ((a>b) && (a!=b));boolean result2 = ((a>b) ||(a!=b));System.out.println("(a>b) && (a!=b)的值是：" + result1);System.out.println("(a>b) ||(a!=b)的值是：" + result2);} }

按位運算符

public class Test {public static void main(String[] args) {int i = 46;int j = 97;char c = 'a';System.out.println("46 & 97 的值是：" + (i&j));System.out.println("46 & 'a' 的值是：" + (i^c));System.out.println("46 >>1 的值是：" + (i>>1));} }

三元條件運算符

public class Test {public static void main(String[] args) {int i = 46;int j = 97;int z = i>j ? 100 : 200;System.out.println("i>j?100:200 的值是：" + z);} }

實例 - 不用其它變量實現兩個變量互換

import java.util.Scanner; public class Test {public static void main(String[] args) {Scanner scan = new Scanner(System.in);System.out.println("請輸入變量A的值：\n");long A = scan.nextLong();System.out.println("請輸入變狼B的值：\n");long B = scan.nextLong();System.out.println("A="+A+"\tB="+B);System.out.println("執行變量互換...");A = A^B;B = B^A;A = A^B;System.out.println("A="+A+"\tB="+B);} }

實例 - 判斷數字的奇偶性

import java.util.Scanner; public class Test {public static void main(String[] args) {Scanner scan = new Scanner(System.in);System.out.println("請輸入一個整數：");long number = scan.nextLong();String check = (number%2 == 0) ? "這個數字是：偶數" : "這個數字是：奇數";System.out.println(check);} }

自動類型轉換

public class Test {public static void main(String[] args) {float number1 = 45f;int number2 = 152;System.out.println(number1+number2);} }

public class Test {public static void main(String[] args) {byte mybyte = 127;int myint = 150;float myfloat = 452.12f;char mychar = 10;double mydouble = 45.46546;//將運算結果輸出System.out.println("127 + 452.12 = " + (mybyte+myfloat));System.out.println("127*150 = " + (mybyte*myint));System.out.println("127/10 = " + (mybyte/mychar));System.out.println("45.46546+10 = " + (mydouble+mychar));} }

強制類型轉換

public class Test {public static void main(String[] args) {int a = (int) 45.23;long y = (long)456.6F;int b = (int)'a';System.out.println("a = " + a);System.out.println("y = " + y);System.out.println("b = " + b);} }

實例 - 類型轉換

public class Test {public static void main(String[] args) {int intNum = 4;float floatNum = 9.5F;floatNum /= intNum; //自動類型轉換System.out.println("9.5F/4 = " + floatNum);double numX = 4.88;double numY = 78.83;int numZ = (int)numX + (int)numY; //強制類型轉換System.out.println("4.88 + 78.83 = " + numZ);char charVar = 'T';int intVar = (int) charVar;System.out.println("將字符T轉換成int型變量是：" + intVar);int num1 = 34;double num2 = (double) num1/3;System.out.println("34的三分之一是："+num2);} }

注釋?
- 單行
- 多行
- 文檔注釋

public class Test {public static void main(String[] args) {// 單行注釋/** 多行注釋1* 多行注釋2*//*** 文檔注釋*/} }

實例 - 判斷某一年是否是閏年

import java.util.Scanner; public class Test {public static void main(String[] args) {Scanner scan = new Scanner(System.in);System.out.println("請輸入一個年份：");long year = scan.nextLong();if(year%4==0 && year%100!=0 || year%400==0) {System.out.println(year + "年是閏年！");}else {System.out.println(year + "年不是閏年！");}} }

實例 - 求球形的體積

import java.util.Scanner; public class Test {public static void main(String[] args) {Scanner scan = new Scanner(System.in);System.out.println("請輸入球形的半徑：");double r = scan.nextDouble();final double PI = 3.1415926;double volume = 4.0/3.0*PI*r*r*r;System.out.println("球形的半徑是：" + r);System.out.println("圓周率是：" + PI);System.out.println("球形的體積是：" + volume);} }

復合語句

public class Test {public static void main(String[] args) {int y = 40;System.out.println("輸出y的值：" + y);int z = 245;boolean b;// 復合語句{b = y>z;System.out.println("y>z城里嗎：" + b);}} } from: http://blog.csdn.net/xuezhisdc/article/details/52174220 《新程序員》：云原生和全面數字化實踐50位技術專家共同創作，文字、視頻、音頻交互閱讀

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