浅谈浅克隆（shallow clone）和 深克隆（deep clone）

区别就在于是否对对象中的引用变量所指向的对象进行拷贝。

1.浅克隆/浅复制/浅拷贝

　　浅拷贝是指在拷贝对象时，对于基本数据类型的变量会重新复制一份，而对于引用类型的变量只是对引用进行拷贝，没有对引用指向的对象进行拷贝。

2.深克隆/深复制/深拷贝

　　深拷贝是指在拷贝对象时，同时会对引用指向的对象进行拷贝。

示例代码：

import java.util.Date;

class Wife implements Cloneable {
    private String name;
    private Date birthday;
    
    public Wife(){
    }
    
    public Wife(String name, Date birthday) {
        this.name = name;
        this.birthday = birthday;
    }

    public Date getBirthday(){
        return birthday;
    }
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    public String toString() {
        return "Wife [name=" + name + ", birthday=" + birthday + "]";
    }
    
}

class Husband implements Cloneable {
    private String name;
    private Wife wife;
    
    public Husband(){
    }

    public Husband(String name, Wife wife) {
        this.name = name;
        this.wife = wife;
    }

    public Wife getWife() {
        return wife;
    }

    public void setWife(Wife wife) {
        this.wife = wife;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    /**
     * 浅克隆一个对象
     * @throws CloneNotSupportedException 
     */
    public Object shallowClone() throws CloneNotSupportedException {
        return super.clone();
    }
    /**
     * 利用串行化深克隆一个对象，把对象以及它的引用读到流里，在写入其他的对象
     * @return
     * @throws Exception
     */
    public Object deepClone() throws Exception {
        Husband husband = (Husband) super.clone();
        husband.wife = (Wife) this.wife.clone();
        return husband;
    }
}

public class Test {
    public static void main(String[] args) throws Exception{
        //浅克隆
        Wife w1 = new Wife("曹夫人", new Date());
        Husband h1 = new Husband("曹先生", w1);
        Husband h2 = (Husband) h1.shallowClone();
        
        System.out.println("原型对象：" + h1.getName() + "--" + h1.getWife());
        System.out.println("克隆对象：" + h2.getName() + "--" + h2.getWife());
        
        w1.setName("张夫人");
        
        System.out.println("
--------------------------修改克隆对象的属性值后---------------------------
");
        
        System.out.println("原型对象：" + h1.getName() + "--" + h1.getWife());
        System.out.println("克隆对象：" + h2.getName() + "--" + h2.getWife());
        
        System.out.println("
---------------------------------------------------------------------
");
        
        //深克隆
        Wife w2 = new Wife("曹夫人", new Date());
        Husband h3 = new Husband("曹先生", w2);
        Husband h4 = (Husband) h3.deepClone();
        
        System.out.println("原型对象：" + h3.getName() + "--" + h3.getWife());
        System.out.println("克隆对象：" + h4.getName() + "--" + h4.getWife());
        
        w2.setName("张夫人");
        
        System.out.println("
--------------------------修改克隆对象的属性值后---------------------------
");
        
        System.out.println("原型对象：" + h3.getName() + "--" + h3.getWife());
        System.out.println("克隆对象：" + h4.getName() + "--" + h4.getWife());
        
        
    }
}

控制台输出：

原型对象：曹先生--Wife [name=曹夫人, birthday=Mon Jan 15 18:00:35 CST 2018]
克隆对象：曹先生--Wife [name=曹夫人, birthday=Mon Jan 15 18:00:35 CST 2018]

--------------------------修改克隆对象的属性值后---------------------------

原型对象：曹先生--Wife [name=张夫人, birthday=Mon Jan 15 18:00:35 CST 2018]
克隆对象：曹先生--Wife [name=张夫人, birthday=Mon Jan 15 18:00:35 CST 2018]

---------------------------------------------------------------------

原型对象：曹先生--Wife [name=曹夫人, birthday=Mon Jan 15 18:00:35 CST 2018]
克隆对象：曹先生--Wife [name=曹夫人, birthday=Mon Jan 15 18:00:35 CST 2018]

--------------------------修改克隆对象的属性值后---------------------------

原型对象：曹先生--Wife [name=张夫人, birthday=Mon Jan 15 18:00:35 CST 2018]
克隆对象：曹先生--Wife [name=曹夫人, birthday=Mon Jan 15 18:00:35 CST 2018]