Java浅拷贝和深拷贝概念以及实现

时间：2016-02-20 20:15:56 阅读：266 评论：0 收藏：0 [点我收藏+]

Java浅拷贝和深拷贝概念以及实现

在Java语言中，因为有引用类型的变量，所以也会有浅拷贝与深拷贝的区别

对于Java中的基础类型byte boolean char short int long float double不需要区分深拷贝和浅拷贝

下面通过一个例子解释深拷贝和浅拷贝

有个Person类如下：

 1 class Person implements Cloneable {
 2     private String name;
 3     private int age; 5 
 6     public Person(String name, int age{
 7         this.name = name;
 8         this.age = age;10     }
 9 
10     @Override
11     public String toString() {
12         return "Person [name=" + name + ", age=" + age + "]";
13     }
14 }

Person curry= new Person("curry", 27) ;

Person curry2 = curry.clone() ;

内存中的模型如下图

技术分享

此时 curry和curry2出两个person对象的name属性值都为curry，且当curry2.setName("kobe") ;时，curry.getName() 也返回"kobe"

这就是浅拷贝

技术分享

此时为深拷贝，再次调用curry2.setName("kobe") ; 不会发生之前的情况

介绍的深拷贝和浅拷贝的概念后，通过实际例子来实现深拷贝和浅拷贝

浅拷贝代码示例

package priv.jack.jdk.demo;

/**
 * 浅拷贝
 * @author Jack
 *
 */
public class ShallowCopy {

    public static void main(String[] args) throws Exception {
        Wallet wallet = new Wallet("LV", 10000);
        Person p1 = new Person("curry", 28, wallet);
        Person p2 = (Person) p1.clone();
        p2.getWallet().setName("保罗");
        p2.getWallet().setMoney(60);
        p2.setName("stu");
        p2.setAge(30);
        System.out.println(p1.toString());
        System.out.println(p2.toString());
    }

}

class Wallet implements Cloneable {
    private String name;
    private long money;

    public Wallet(String name, int money) {
        this.name = name;
        this.money = money;
    }

    @Override
    public String toString() {
        return "Wallet [name=" + name + ", money=" + money + "]";
    }

    public String getName() {
        return name;
    }

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

    public long getMoney() {
        return money;
    }

    public void setMoney(long money) {
        this.money = money;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

}

class Person implements Cloneable {
    private String name;
    private int age;
    private Wallet wallet;

    public Person(String name, int age, Wallet wallet) {
        this.name = name;
        this.age = age;
        this.wallet = wallet;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + ", p=" + wallet + "]";
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Wallet getWallet() {
        return wallet;
    }

    public void setWallet(Wallet wallet) {
        this.wallet = wallet;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

}

运行结果如下

Person [name=curry, age=28, p=Wallet [name=保罗, money=60]]
Person [name=stu, age=30, p=Wallet [name=保罗, money=60]]

钱包的名称和金额都变了，说明两个人公用一个钱包，这样不好吧

深拷贝实例一

package priv.jack.jdk.demo;

/**
 * 深拷贝
 * @author Jack
 *
 */
public class DeepCopy1 {

    public static void main(String[] args) throws Exception {
        Wallet1 Wallet1 = new Wallet1("LV", 10000);
        Person1 p1 = new Person1("curry", 28, Wallet1);
        Person1 p2 = (Person1) p1.clone();
        p2.getWallet1().setName("保罗");
        p2.getWallet1().setMoney(60);
        p2.setName("stu");
        p2.setAge(30);
        System.out.println(p1.toString());
        System.out.println(p2.toString());
    }

}

class Wallet1 implements Cloneable {
    private String name;
    private long money;

    public Wallet1(String name, int money) {
        this.name = name;
        this.money = money;
    }

    @Override
    public String toString() {
        return "Wallet1 [name=" + name + ", money=" + money + "]";
    }

    public String getName() {
        return name;
    }

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

    public long getMoney() {
        return money;
    }

    public void setMoney(long money) {
        this.money = money;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

}

class Person1 implements Cloneable {
    private String name;
    private int age;
    private Wallet1 wallet;

    public Person1(String name, int age, Wallet1 Wallet1) {
        this.name = name;
        this.age = age;
        this.wallet = Wallet1;
    }

    @Override
    public String toString() {
        return "Person1 [name=" + name + ", age=" + age + ", p=" + wallet + "]";
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Wallet1 getWallet1() {
        return wallet;
    }

    public void setWallet1(Wallet1 wallet) {
        this.wallet = wallet;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Person1 p =(Person1) super.clone() ;
        p.wallet = (Wallet1) wallet.clone() ;
        return p ;
    }

}

运行结果如下：

Person1 [name=curry, age=28, p=Wallet1 [name=LV, money=10000]]
Person1 [name=stu, age=30, p=Wallet1 [name=保罗, money=60]]

深拷贝实例二

package priv.jack.jdk.demo;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

/**
 * 深拷贝
 * @author Jack
 *
 */
public class DeepCopy2{

    public static void main(String[] args) throws Exception {
        Wallet2 wallet = new Wallet2("LV", 10000);
        Person2 p1 = new Person2("curry", 28, wallet);
        Person2 p2 = (Person2) p1.deepClone();
        p2.getWallet2().setName("保罗");
        p2.getWallet2().setMoney(60);
        p2.setName("stu");
        p2.setAge(30);
        System.out.println(p1.toString());
        System.out.println(p2.toString());
    }

}

class Wallet2 implements Serializable {
    
    private static final long serialVersionUID = 5496170174896341934L;
    
    private String name;
    private long money;

    public Wallet2(String name, int money) {
        this.name = name;
        this.money = money;
    }

    @Override
    public String toString() {
        return "Wallet2 [name=" + name + ", money=" + money + "]";
    }

    public String getName() {
        return name;
    }

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

    public long getMoney() {
        return money;
    }

    public void setMoney(long money) {
        this.money = money;
    }

}

class Person2 implements Serializable {
    
    private static final long serialVersionUID = -7860166025209047988L;
    
    private String name;
    private int age;
    private Wallet2 wallet;

    public Person2(String name, int age, Wallet2 Wallet2) {
        this.name = name;
        this.age = age;
        this.wallet = Wallet2;
    }

    @Override
    public String toString() {
        return "Person2 [name=" + name + ", age=" + age + ", p=" + wallet + "]";
    }
    
    public Object deepClone() throws Exception {
        ByteArrayOutputStream bao = new ByteArrayOutputStream() ;
        ObjectOutputStream oo = new ObjectOutputStream(bao) ;
        oo.writeObject(this);
        ByteArrayInputStream bai = new ByteArrayInputStream(bao.toByteArray()) ;
        ObjectInputStream oi = new ObjectInputStream(bai) ;
        Object obj = oi.readObject() ;
        return obj ;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public Wallet2 getWallet2() {
        return wallet;
    }

    public void setWallet2(Wallet2 wallet) {
        this.wallet = wallet;
    }

}

运行结果如下：

Person2 [name=curry, age=28, p=Wallet2 [name=LV, money=10000]]
Person2 [name=stu, age=30, p=Wallet2 [name=保罗, money=60]]

OK，done。

Java浅拷贝和深拷贝概念以及实现

原文：http://www.cnblogs.com/jack2013/p/5200737.html

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