無論是在java面試過程中，還是在與各種老鳥交流的過程中，對java對象的深淺拷貝，都是一個繞不開的問題，這個問題看似很容易，卻是大多數(shù)人用來區(qū)分小白的標準問題。現(xiàn)在對該問題進行說明。

1.定義

淺克隆（拷貝）：復(fù)制一個對象的實例，但是這個對象中包含的其它的對象還是共用的。一般用super.clone()方法，clone的對象就是淺克隆。
深克隆（拷貝）：復(fù)制一個對象的實例，而且這個對象中包含的其它的對象也要復(fù)制一份。如果使用clone()，那么需要對clone方法進行重寫，復(fù)制一個對象super.clone()，之后再一一對屬性進行復(fù)制。這樣顯得非常冗余，幸好，在java中還可以通過流來實現(xiàn)。但是注意，對象需要實現(xiàn)Serializable接口。

2.舉例

有如下類Husband, Husband又引用了Wife。

類結(jié)構(gòu)圖

Wife類

package com.dhb.CloneTest;

import lombok.Data;

import java.io.Serializable;
import java.util.Date;

@Data
public class Wife implements Serializable {

    private String name;

    private Date birthday;

    public Wife() {
        this.name = "思思";
        this.birthday = new Date();
    }

    public Wife(String name, Date birthday) {
        this.name = name;
        this.birthday = birthday;
    }
}

Husband類

package com.dhb.CloneTest;

import lombok.Data;

import java.io.*;
import java.util.Date;

@Data
public class Husband implements Cloneable,Serializable {

    private Wife wife;

    private Date birthday;

    public Husband() {
        this.wife = new Wife();
        this.birthday = new Date();
    }

    public Husband(Wife wife, Date birthday) {
        this.wife = wife;
        this.birthday = birthday;
    }

    public Object clone() {
        Husband husband = null;
        try {
            husband = (Husband) super.clone();
        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }finally {
            return  husband;
        }
    }

    public Object  deepClone() throws IOException, ClassNotFoundException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(this);
        ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
        ObjectInputStream ois = new ObjectInputStream(bis);
        return  ois.readObject();
    }

}

在Husband類中存在clone和deepClone方法。現(xiàn)在對這兩個方法進行測試。

package com.dhb.CloneTest;

import java.io.IOException;

public class CloneTest {

    public static void main(String[] args) {

        try {
            Husband husband = new Husband();
            System.out.println("husband birthday is :"+husband.getBirthday());
            System.out.println("wife birthday is :"+husband.getWife().getBirthday());
            System.out.println("***********************************************");
            Husband husband1 = (Husband) husband.clone();
            System.out.println("husband1 birthday is :"+husband1.getBirthday());
            System.out.println("wife birthday is :"+husband1.getWife().getBirthday());
            System.out.println("***********************************************");
            System.out.println("husband 是否相同："+(husband == husband1));
            System.out.println("wife 是否相同："+(husband.getWife() == husband1.getWife()));

            System.out.println("***********************************************");
            Husband husband2 = (Husband) husband.deepClone();
            System.out.println("husband2 birthday is :"+husband2.getBirthday());
            System.out.println("wife birthday is :"+husband2.getWife().getBirthday());
            System.out.println("***********************************************");
            System.out.println("husband 是否相同："+(husband == husband2));
            System.out.println("wife 是否相同："+(husband.getWife() == husband2.getWife()));

        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

    }

}

運行結(jié)果：

husband birthday is :Mon Aug 07 19:03:38 CST 2017
wife birthday is :Mon Aug 07 19:03:38 CST 2017
***********************************************
husband1 birthday is :Mon Aug 07 19:03:38 CST 2017
wife birthday is :Mon Aug 07 19:03:38 CST 2017
***********************************************
husband 是否相同：false
wife 是否相同：true
***********************************************
husband2 birthday is :Mon Aug 07 19:03:38 CST 2017
wife birthday is :Mon Aug 07 19:03:38 CST 2017
***********************************************
husband 是否相同：false
wife 是否相同：false

注：上述代碼中的@Data 是lombak的一個注解。

當(dāng)然，實現(xiàn)深克隆的方法并不局限于流這一種辦法，還可以通過json等其他辦法實現(xiàn)。