java对象克隆之深度克隆 deep clone

克隆技术默认的是浅度克隆，对于包含在对象内部的对象并没有克隆，例如对象stdA包含对象x，克隆后得到对象stdB，也包含对象x，但两个x所指向的数据成员相同。

深度克隆实例如下：

package com.demo;
class Book implements Cloneable{
	private String name;
	private double price;
	public Book(String name, double price){
		this.name = name;
		this.price = price;
	}
	public void setName(String name){
		this.name = name;
	}
	public Object clone() throws CloneNotSupportedException{
		return super.clone();
	}
	public String toString(){
		return "书名："+ this.name + " 单价：" + this.price;
	}
}
class Student implements Cloneable{
	private String name;
	private String sex;
	private Book book;
	public Student(String name, String sex, Book book){
		this.name = name;
		this.sex = sex;
		this.book = book;
	}
	public Object clone() throws CloneNotSupportedException {
		Student std = null;
		//克隆当前对象
		std = (Student)super.clone();
		//克隆当前对象所包含的对象
		std.book = (Book)book.clone();
		return std;
		//return super.clone();
	}
	
	public void setName(String name){
		this.name = name;
	}
	public void setBook(Book book){
		this.book = book;
	}
	public String toString(){
		return "姓名："+name + ", 性别" + sex + "\n借的书：" + this.book.toString();
	}
}
public class Demo {
public static void main(String[] args) throws Exception {
	Book book = new Book("理想国", 35);
    Student stdA = new Student("梅西", "男", book);
    //采用赋值方式
    Student stdB = stdA;
    stdA.setName("李娜");
    System.out.println("stdA:"+ stdA + "\nstdB:" + stdB);
    stdB =  (Student) stdA.clone();
    stdA.setName("梅西");
    System.out.println("克隆之后：");
    System.out.println("stdA: " + stdA + "\nstdB " + stdB);

}

}

输出结果：

stdA:姓名：李娜, 性别男
借的书：书名：理想国 单价：35.0
stdB:姓名：李娜, 性别男
借的书：书名：理想国 单价：35.0
克隆之后：
stdA: 姓名：梅西, 性别男
借的书：书名：理想国 单价：35.0
stdB 姓名：李娜, 性别男
借的书：书名：理想国 单价：35.0

深度克隆步骤1.克隆当前对象；2克隆当前对象所引用的对象；3返回当前对象