JAVA 对象拷贝

1.Java里的clone分为： 
A:浅复制（浅克隆）: 浅复制仅仅复制所考虑的对象，而不复制它所引用的对象。 
b:深复制（深克隆）：深复制把要复制的对象所引用的对象都复制了一遍。 
Java中对象的克隆,为了获取对象的一份拷贝，我们可以利用Object类的clone()方法。必须要遵循下面三点 
1.在派生类中覆盖基类的clone()方法，并声明为public【Object类中的clone()方法为protected的】。 
2.在派生类的clone()方法中，调用super.clone()。 
3.在派生类中实现Cloneable接口。 

Object类里的clone方法是浅复制（浅克隆） 

浅复制（浅克隆）的例子如下： 

public class CloneTest{public static void main(String[] args) throws Exception{// teacher对象将被clone出来的Student对象共享.Teacher teacher = new Teacher();teacher.setAge(40);teacher.setName("Teacher zhang");Student student1 = new Student();student1.setAge(20);student1.setName("zhangsan");student1.setTeacher(teacher);// 复制出来一个对象student2Student student2 = (Student) student1.clone();System.out.println(student2.getAge());System.out.println(student2.getName());System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());// 修改student2的引用对象student2.getTeacher().setAge(50);student2.getTeacher().setName("Teacher Li");System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());}}class Teacher{public int age;public String name;public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getName(){return name;}public void setName(String name){this.name = name;}}class Student implements Cloneable{public int age;public String name;public Teacher teacher;public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getName(){return name;}public void setName(String name){this.name = name;}public Teacher getTeacher(){return teacher;}public void setTeacher(Teacher teacher){this.teacher = teacher;}@Overridepublic Object clone() throws CloneNotSupportedException{return super.clone();}}输出结果为：20zhangsan~~~~~~~~~~~~~~~~~~~~~~40Teacher zhang~~~~~~~~~~~~~~~~~~~~~~50Teacher Li

2.深复制（深Clone）例子：

public class DeepCloneTest{public static void main(String[] args) throws Exception{// teacher对象将不被clone出来的Student对象共享.Teacher teacher = new Teacher();teacher.setAge(40);teacher.setName("Teacher zhang");Student student1 = new Student();student1.setAge(20);student1.setName("zhangsan");student1.setTeacher(teacher);// 复制出来一个对象student2Student student2 = (Student) student1.clone();System.out.println(student2.getAge());System.out.println(student2.getName());System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());// 修改student2的引用对象student2.getTeacher().setAge(50);student2.getTeacher().setName("Teacher Li");System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());}}class Teacher implements Cloneable{public int age;public String name;public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getName(){return name;}public void setName(String name){this.name = name;}@Overridepublic Object clone() throws CloneNotSupportedException{return super.clone();}}class Student implements Cloneable{public int age;public String name;public Teacher teacher;public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getName(){return name;}public void setName(String name){this.name = name;}public Teacher getTeacher(){return teacher;}public void setTeacher(Teacher teacher){this.teacher = teacher;}@Overridepublic Object clone() throws CloneNotSupportedException{Student student = (Student) super.clone();// 将引用的对象teacher也clone下student.setTeacher((Teacher) (student.getTeacher().clone()));return student;}}输出结果为：20zhangsan~~~~~~~~~~~~~~~~~~~~~~40Teacher zhang~~~~~~~~~~~~~~~~~~~~~~40Teacher zhang

3.利用序列化来做深复制,把对象写到流里的过程是序列化（Serilization）过程，而把对象从流中读出来的过程则叫做反序列化（Deserialization）过程。应当指出的是，写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。，利用这个特性，可以做深拷贝 。

import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.io.Serializable;//利用序列化来做深复制//深clonepublic class DeepCloneTest{public static void main(String[] args) throws Exception{// teacher对象将不被clone出来的Student对象共享.Teacher teacher = new Teacher();teacher.setAge(40);teacher.setName("Teacher zhang");Student student1 = new Student();student1.setAge(20);student1.setName("zhangsan");student1.setTeacher(teacher);// 复制出来一个对象student2Student student2 = (Student) student1.deepCopy();System.out.println(student2.getAge());System.out.println(student2.getName());System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());// 修改student2的引用对象student2.getTeacher().setAge(50);student2.getTeacher().setName("Teacher Li");System.out.println("~~~~~~~~~~~~~~~~~~~~~~");System.out.println(student1.getTeacher().getAge());System.out.println(student1.getTeacher().getName());}}class Teacher implements Serializable{private static final long serialVersionUID = -8834559347461591191L;public int age;public String name;public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getName(){return name;}public void setName(String name){this.name = name;}}class Student implements Serializable{// serialVersionUID// 如果你的对象序列化后存到硬盘上面后，可是后来你却更改了类的field(增加或减少或改名)，当你反序列化时，就会出现Exception的，这样就会造成不兼容性的问题。// 但当serialVersionUID相同时，它就会将不一样的field以type的缺省值赋值(如int型的是0,String型的是null等)，这个可以避开不兼容性的问题。所以最好给serialVersionUID赋值private static final long serialVersionUID = 7991552226614088458L;public int age;public String name;public Teacher teacher;public int getAge(){return age;}public void setAge(int age){this.age = age;}public String getName(){return name;}public void setName(String name){this.name = name;}public Teacher getTeacher(){return teacher;}public void setTeacher(Teacher teacher){this.teacher = teacher;}public Object deepCopy() throws Exception{// 将该对象序列化成流,因为写在流里的是对象的一个拷贝，而原对象仍然存在于JVM里面。所以利用这个特性可以实现对象的深拷贝ByteArrayOutputStream bos = new ByteArrayOutputStream();ObjectOutputStream oos = new ObjectOutputStream(bos);oos.writeObject(this);// 将流序列化成对象ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());ObjectInputStream ois = new ObjectInputStream(bis);return ois.readObject();}}输出结果为：20zhangsan~~~~~~~~~~~~~~~~~~~~~~40Teacher zhang~~~~~~~~~~~~~~~~~~~~~~40Teacher zhang

原文地址：http://blog.csdn.net/jdluojing/article/details/6963112/