java 对象创建过程_5种创建Java对象的方式
在本篇文章中，將介紹5種創(chuàng)建Java對(duì)象的方式。類是創(chuàng)建對(duì)象的基本模板，接下來將介紹5種不同的方式，利用Java類來實(shí)例化Java對(duì)象。
1. 使用new關(guān)鍵字
? 采用new關(guān)鍵字實(shí)例化對(duì)象是Java中最為常見的方法，下面是采用new關(guān)鍵字實(shí)例化對(duì)象的示例。在開始之前，我們先準(zhǔn)備好一個(gè)Java類：Student.java。
package com.ramostear.oops;public class Student{ private String name; private String nickname; public Student(String name,String nickname){ this.name = name; this.nickname = nickname; } public String getName(){ return name; } public void setName(String name){ this.name = name; } public String getNickname(){ return nickname; } public void setNickname(String nickname){ this.nickname = nickname; }}接下來，我們通過new關(guān)鍵字來創(chuàng)建幾個(gè)學(xué)生：
package com.ramostear.oops;public class TestNewStudent{ public static void main(String[] args){ Student zhangsan = new Student("Zhangsan","張三"); Student lisi = new Student(); lisi.setName("Lisi"); lisi.setNickname("李四")； }}2. 使用Class類的newInstance()方法
? 首先，我們可以通過Class.forName()方法動(dòng)態(tài)加載目標(biāo)類，然后再調(diào)用newInstance()方法，動(dòng)態(tài)實(shí)例化對(duì)象。同理，在開始之前，我們需要準(zhǔn)備一個(gè)目標(biāo)類：Student.java。
package com.ramostear.oops;public class Student{ private String name = "Zhangsan"; private String nickname = "張三"; public Student(){ super(); } public Student(String name,String nickname){ super(); this.name = name; this.nickname = nickname; } public String getName(){ return name; } public void setName(String name){ this.name = name; } public String getNickname(){ return nickname; } public void setNickname(String nickname){ this.nickname = nickname; }}接下來，將演示如何通過newInstance()方法來創(chuàng)建新的對(duì)象：
package com.ramostear.oops;public class TestUseNewInstanceMethod{ public static void main(String[] args){ try{ String className = "com.ramostear.oops.Student"; Class clz = Class.forName(className); Student student = (Student) clz.newInstance(); System.out.println("student name :"+ student.getName()+", nickname: "+student.getNickname()); }catch(InstantiationException | IllegalAccessException | ClassNotFoundException e){ e.printStackTrace(); } }}運(yùn)行main()方法，將輸出如下信息：
student name :Zhangsan, nickname:張三3. 使用Constructor.newInstance()方法
? 與Class類的newInstance()方法相似，我們還可以使用java.lang.reflect.Constructor類的newInstance()方法來創(chuàng)建新的對(duì)象。同樣，我們先準(zhǔn)備一個(gè)目標(biāo)類：
package com.ramostear.oops;public class Student{ private String name = "Constructor"; private String nickname = "構(gòu)造器"; public Student(){ super(); } public Student(String name,String nickname){ super(); this.name = name; this.nickname = nickname; } public String getName(){ return name; } public void setName(String name){ this.name = name; } public String getNickname(){ return nickname; } public void setNickname(String nickname){ this.nickname = nickname; }}接下來，我們看看如何使用Constructor的newInstance()方法創(chuàng)建新的對(duì)象：
package com.ramostear.oops;import java.lang.reflect.Constructor;import java.lang.reflect.InvocationTargetException;public class UseConstructorNewInstanceMethod{ public static void main(String[] args){ Constructor studentConstructor; try{ studentConstructor = Student.class.getConstructor(); Student student = studentConstructor.newInstance(); System.out.println("student name :"+ student.getName()+", nickname: "+student.getNickname()); }catch(InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException | NoSuchMethodException | SecurityException e){ e.printStackTrace(); } } }執(zhí)行main()方法，將在控制臺(tái)輸出如下信息：
student name:Constructor, nickname:構(gòu)造器4. 使用反序列化
? 如果要使用反序列化創(chuàng)建對(duì)象，則目標(biāo)類首先要實(shí)現(xiàn)Serializable接口。Serializable是一個(gè)標(biāo)記接口。在本次示例中，我們先創(chuàng)建一個(gè)Student對(duì)象，并將其保存到data.txt文件中，然后在通過反序列化操作，讀取data.txt中的數(shù)據(jù)，并創(chuàng)建新的對(duì)象。
package com.ramostear.oops;import java.io.Serializable;public class Student implements Serializable{ private String name; private String nickname; public Student() { super(); } public Student(String name, String nickname) { super(); this.name = name; this.nickname = nickname; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getNickname() { return nickname; } public void setNickname(String nickname) { this.nickname = nickname; }}接下來，將通過一個(gè)簡(jiǎn)單的示例，演示如何使用反序列化的方式創(chuàng)建新的對(duì)象：
package com.ramostear.oops;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;public class StudentDemo { public static void main(String[] args) { String filePath = "data.txt"; Student student1 = new Student("Deserialization", "反序列化"); try { FileOutputStream fileOutputStream = new FileOutputStream(filePath); ObjectOutputStream outputStream = new ObjectOutputStream(fileOutputStream); outputStream.writeObject(student1); outputStream.flush(); outputStream.close(); FileInputStream fileInputStream = new FileInputStream(filePath); ObjectInputStream inputStream = new ObjectInputStream(fileInputStream); Student student2 = (Student) inputStream.readObject(); inputStream.close(); System.out.println("Student name:"+student2.getName()+", nickname:"+student2.getNickname()); } catch (Exception ee) { ee.printStackTrace(); } }}執(zhí)行上述代碼，將在控制臺(tái)輸出如下信息：
Student name:Deserialization,nickname:反序列化5. 使用對(duì)象克隆創(chuàng)建新的對(duì)象
? clone()方法可以創(chuàng)建現(xiàn)有對(duì)象的副本，但在使用clone()方法前，需保證模板類實(shí)現(xiàn)了Cloneable接口，Cloneable接口也是一個(gè)標(biāo)記類接口。下面是使用克隆方式創(chuàng)建新對(duì)象的完整示例：
package net.javaguides.corejava.oops;import java.io.Serializable;public class Student implements Cloneable { private String name; private String nickname; public Student() { super(); } public Student(String name, String nickname) { super(); this.name = name; this.nickname = nickname; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getNickname() { return nickname; } public void setNickname(String nickname) { this.nickname = nickname; } public static void main(String args[]) { Student stu1 = new Student("Clone", "克隆"); try { Student stu2 = (Student) stu1.clone(); System.out.println("Student name :"+stu2.getName()+",nickname:"+stu2.getNickanme()); } catch (CloneNotSupportedException e) { e.printStackTrace(); } }}運(yùn)行上述代碼，控制臺(tái)將輸出如下信息：
Student name： Clone,nickname:克隆總結(jié)
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