Java实现深拷贝和浅拷贝

Posted 2020-09-03 ~~Cc

1.类实现Cloneable才可以进行对象拷贝

2.Cloneable只实现浅拷贝，需要实现深拷贝的必须要重写clone()方法

3.利用反序列化也可以实现深拷贝，但是反序列化耗时较长

n.浅拷贝是指拷贝对象时只拷贝对象本身和其基本变量及引用变量，不拷贝对象中引用指向的对象，深拷贝反之

 

4.可以浅拷贝的对象类

 1 package deepCopy;
 2 
 3 import java.io.Serializable;
 4 
 5 public class UserShallowClone implements Cloneable,Serializable{
 6     
 7     /**
 8      * 
 9      */
10     private static final long serialVersionUID = 222;
11     private int age;
12     private String name;
13     private House house;
14     
15     public UserShallowClone(int age, String name, House house) {
16         super();
17         this.age = age;
18         this.name = name;
19         this.house = house;
20     }
21     
22     
23     public int getAge() {
24         return age;
25     }
26 
27 
28     public void setAge(int age) {
29         this.age = age;
30     }
31 
32 
33     public String getName() {
34         return name;
35     }
36 
37 
38     public void setName(String name) {
39         this.name = name;
40     }
41 
42 
43     public House getHouse() {
44         return house;
45     }
46 
47 
48     public void setHouse(House house) {
49         this.house = house;
50     }
51 
52 
53     @Override
54     protected Object clone() throws CloneNotSupportedException {
55         // TODO Auto-generated method stub
56         return super.clone();
57     }
58 
59 }

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5.可以深拷贝的对象类

 1 package deepCopy;
 2 
 3 public class UserDeepClone implements Cloneable{
 4 
 5     private int age;
 6     private String name;
 7     private House house;
 8     
 9     public UserDeepClone(int age, String name, House house) {
10         super();
11         this.age = age;
12         this.name = name;
13         this.house = house;
14     }
15     
16     
17     public int getAge() {
18         return age;
19     }
20 
21 
22     public void setAge(int age) {
23         this.age = age;
24     }
25 
26 
27     public String getName() {
28         return name;
29     }
30 
31 
32     public void setName(String name) {
33         this.name = name;
34     }
35 
36 
37     public House getHouse() {
38         return house;
39     }
40 
41 
42     public void setHouse(House house) {
43         this.house = house;
44     }
45 
46 
47     @Override
48     protected Object clone() throws CloneNotSupportedException {
49         UserDeepClone userNew = (UserDeepClone)super.clone();
50         userNew.house = (House) house.clone();
51         return userNew;
52     }
53     
54 }

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6.House类

 1 package deepCopy;
 2 
 3 import java.io.Serializable;
 4 
 5 public class House implements Cloneable,Serializable{
 6     
 7     /**
 8      * 
 9      */
10     private static final long serialVersionUID = 33;
11     private int zipCode;
12 
13     public House(int zipCode) {
14         super();
15         this.zipCode = zipCode;
16     }
17 
18     public int getZipCode() {
19         return zipCode;
20     }
21 
22     public void setZipCode(int zipCode) {
23         this.zipCode = zipCode;
24     }
25 
26     @Override
27     protected Object clone() throws CloneNotSupportedException {
28         // TODO Auto-generated method stub
29         return super.clone();
30     }
31     
32     
33 }

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7.测试类

package deepCopy;

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

public class Test {
    public static void main(String[] args) throws CloneNotSupportedException, IOException, ClassNotFoundException
    {
        //deep copy
        long deepClone = System.currentTimeMillis();
        House house = new House(1010);
        UserDeepClone userDeep = new UserDeepClone(11, "CC", house);
        UserDeepClone userDeepCopy = (UserDeepClone) userDeep.clone();
        System.out.println("deep copy by cloneable speeds " +(System.currentTimeMillis()-deepClone) + "ms");
        System.out.println("Deep Copy----------");
        System.out.println("userDeep" + userDeep
                + ",userSDeepCopy=" + userDeepCopy);
        System.out.println("userDeep house=" + userDeep.getHouse()
                + ",userDeepCopy house=" + userDeepCopy.getHouse());

        System.out.println();
        System.out.println("Shallow Copy----------");
        
        //shallow copy
        long shallowCopy = System.currentTimeMillis();
        UserShallowClone userShallow = new UserShallowClone(12, "CC", house);
        UserShallowClone userShallowCopy = (UserShallowClone) userShallow.clone();
        System.out.println("shallowCopy spends " + (System.currentTimeMillis()-shallowCopy) + "ms");
        System.out.println("userShallow=" + userDeep
                + ",userShallowCopy=" + userDeepCopy);
        System.out.println("userShallow house=" + userShallow.getHouse()
                + ",userShallowCopy house=" + userShallowCopy.getHouse());
        //反序列化深拷贝
        System.out.println();
        long deepSer = System.currentTimeMillis();
        ByteArrayOutputStream bo = new ByteArrayOutputStream();
        ObjectOutputStream oo = new ObjectOutputStream(bo);
        oo.writeObject(userShallow);
        
        ObjectInputStream oi = new ObjectInputStream(new ByteArrayInputStream(bo.toByteArray()));
        UserShallowClone  userDeepSer = (UserShallowClone) oi.readObject();
        System.out.println("deep copy by ser spends " + (System.currentTimeMillis()-deepSer) + "ms");
        System.out.println("deep copy by ser--------------------");
        System.out.println("userShallow=" + userShallow
                +",userDeepSer=" + userDeepSer);
        System.out.println("userShallow house=" + userShallow.getHouse()
                +",userDeepSer house=" + userDeepSer.getHouse());
    }
}

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8.测试结果