Java浅克隆与深克隆

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浅克隆与深克隆
浅克隆的对象与原对象引用不相等，但对象中的对象是相等的
深克隆则是全部不相等

浅克隆的实现
需要该类实现Cloneable接口（该接口无需实现任何方法，只是一个标志），并重写Object类中的clone方法（该方法为protect，只能在其子类中调用），
编写车轮（Wheel）类，代码如下所示：

public class Wheel {    private String size;    public String getSize() {        return size;    }    public void setSize(String size) {        this.size = size;    }}

汽车（Car）类，内含wheel对象，并实现Cloneable接口，重写clone方法，代码如下所示：

public class Car implements Cloneable{    private String color;    private String band;    private Wheel wheel;    public String getColor() {        return color;    }    public void setColor(String color) {        this.color = color;    }    public String getBand() {        return band;    }    public void setBand(String band) {        this.band = band;    }    public Wheel getWheel() {        return wheel;    }    public void setWheel(Wheel wheel) {        this.wheel = wheel;    }    public Object clone(){        Object object = null;        try {            object = super.clone();        } catch (CloneNotSupportedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return object;    }}

测试代码如下：

import java.io.IOException;public class CloneTest {    public static void main(String[] args) throws ClassNotFoundException, IOException {        Car car1 = new Car();        car1.setBand("benz");        car1.setColor("red");        Wheel wheel = new Wheel();        wheel.setSize("14");        car1.setWheel(wheel);        Car car2 = (Car) car1.clone();        // 输出false        System.out.println(car1 == car2);        // 输出true        System.out.println(car1.getWheel() == car2.getWheel());        // car2 band为benz        System.out.println(car2.getBand());        // car2的wheel size为14        System.out.println(car2.getWheel().getSize());    }}

深克隆的实现
有两种方法，第一种需要类实现Serializable序列化接口，对象中的对象也需实现序列化。
Wheel类改造如下：

import java.io.Serializable;public class Wheel implements Serializable {    /**     *      */    private static final long serialVersionUID = -467379705588570699L;    private String size;    public String getSize() {        return size;    }    public void setSize(String size) {        this.size = size;    }}

Car类改造如下：

import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.io.Serializable;public class Car implements Cloneable, Serializable{    /**     *      */    private static final long serialVersionUID = 227203306278742729L;    private String color;    private String band;    private Wheel wheel;    public String getColor() {        return color;    }    public void setColor(String color) {        this.color = color;    }    public String getBand() {        return band;    }    public void setBand(String band) {        this.band = band;    }    public Wheel getWheel() {        return wheel;    }    public void setWheel(Wheel wheel) {        this.wheel = wheel;    }    public Object clone(){        Object object = null;        try {            object = super.clone();        } catch (CloneNotSupportedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return object;    }    // 深度克隆方法，相当于把对象序列化后再读取出来，保留了对象的全部属性并与原对象不相等    public Object deepClone() throws IOException, ClassNotFoundException{        ByteArrayOutputStream baos = new ByteArrayOutputStream();          ObjectOutputStream oos = new ObjectOutputStream(baos);          oos.writeObject(this);          ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());          ObjectInputStream ois = new ObjectInputStream(bais);          return ois.readObject();      }}

测试类如下：

import java.io.IOException;public class CloneTest {    public static void main(String[] args) throws ClassNotFoundException, IOException {        Car car1 = new Car();        car1.setBand("benz");        car1.setColor("red");        Wheel wheel = new Wheel();        wheel.setSize("14");        car1.setWheel(wheel);        Car car2 = (Car) car1.deepClone();        // 输出false        System.out.println(car1 == car2);        // 输出false，说明深克隆成功        System.out.println(car1.getWheel() == car2.getWheel());    }}

深克隆第二种方法，使用json，将对象转为json，再将json转为对象，实现了深克隆，且不需实现任何接口

public Object deepClone2(){    JSONObject json = (JSONObject) JSON.toJSON(this);    return JSON.toJavaObject(json, Person.class);}

但据网友测试，第一种方法较此方法效率略高

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