java 浅复制和深复制

蔚落 2022-06-17 07:59 272阅读 0赞

原文：[http://ttitfly.iteye.com/blog/155422][http_ttitfly.iteye.com_blog_155422]

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：

package com.test;
    
    //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。
    //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。
    
    //[color=red]Object类里的clone方法是浅复制（浅克隆）[/color]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student2
    		Student 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;
    	}
    	@Override
    	public Object clone() throws CloneNotSupportedException {
    		return super.clone();
    	}
    	
    	
    }
    输出结果为：
    20
    zhangsan
    ~~~~~~~~~~~~~~~~~~~~~~
    40
    Teacher zhang
    ~~~~~~~~~~~~~~~~~~~~~~
    50
    Teacher Li

2.深复制（深Clone）例子：

package com.test1;
    
    //深clone
    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student2
    		Student 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;
    	}
    	@Override
    	public 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;
    	}
    	@Override
    	public 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：
    20
    zhangsan
    ~~~~~~~~~~~~~~~~~~~~~~
    40
    Teacher zhang
    ~~~~~~~~~~~~~~~~~~~~~~
    40
    Teacher 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

package com.test3;
    
    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clone
    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student2
    		Student 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：
    20
    zhangsan
    ~~~~~~~~~~~~~~~~~~~~~~
    40
    Teacher zhang
    ~~~~~~~~~~~~~~~~~~~~~~
    40
    Teacher zhang

[http_ttitfly.iteye.com_blog_155422]: http://ttitfly.iteye.com/blog/155422