【GOF23設計模式】_原型模式JAVA233-234

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一、S03E233_01【GOF23設計模式】_原型模式、prototype、淺複製、深複製、Cloneable接口

淺複製

package com.test.prototype;

import java.util.Date;

/**
 * 淺複製
 */
public class Sheep implements Cloneable{//Cloneable爲標記接口
    private String sname;
    private Date birthday;

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object obj = super.clone();//直接調用object對象的clone()方法
        return obj;
    }

    public Sheep() {
    }

    public Sheep(String sname, Date birthday) {
        super();
        this.sname = sname;
        this.birthday = birthday;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
}

package com.test.prototype;

import java.util.Date;
/**
 * 測試原型模式(淺複製)
 */
public class Client {
    public static void main(String[] args) throws Exception {
        Date date = new Date(3333332323L);
        Sheep s1 = new Sheep("少利", date);
        Sheep s2 = (Sheep) s1.clone();

        System.out.println(s1);
        System.out.println(s1.getSname());
        System.out.println(s1.getBirthday());
        date.setTime(332324355555555L);//淺複製：s1和s2指向同一date對象的地址，一改全改
        System.out.println(s1.getBirthday());//s1.getBirthday() == s2.getBirthday()

        s2.setSname("多利");
        System.out.println(s2);
        System.out.println(s2.getSname());
        System.out.println(s2.getBirthday());
    }
}

控制檯輸出：s1修改時間後，s2的也跟着改(Fri Dec 10 00:59:15 CST 12500)

com.test.prototype.Sheep@1db9742
少利
Sun Feb 08 21:55:32 CST 1970
Fri Dec 10 00:59:15 CST 12500
com.test.prototype.Sheep@647e05
多利
Fri Dec 10 00:59:15 CST 12500

深複製

package com.test.prototype;

import java.util.Date;

/**
 * 深複製
 */
public class Sheep2 implements Cloneable{//Cloneable爲標記接口
    private String sname;
    private Date birthday;

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object obj = super.clone();//直接調用object對象的clone()方法

        //添加如下代碼實現深複製(Deep Clone)
        Sheep2 s = (Sheep2) obj;
        s.birthday = (Date) this.birthday.clone();//屬性克隆！

        return obj;
    }

    public Sheep2() {
    }

    public Sheep2(String sname, Date birthday) {
        super();
        this.sname = sname;
        this.birthday = birthday;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
}

package com.test.prototype;

import java.util.Date;
/**
 * 測試原型模式(深複製)
 */
public class Client2 {
    public static void main(String[] args) throws Exception {
        Date date = new Date(3333332323L);
        Sheep2 s1 = new Sheep2("少利", date);
        Sheep2 s2 = (Sheep2) s1.clone();

        System.out.println(s1);
        System.out.println(s1.getSname());
        System.out.println(s1.getBirthday());
        date.setTime(332324355555555L);//淺複製：s1和s2指向同一date對象的地址，一改全改
        System.out.println(s1.getBirthday());//s1.getBirthday() == s2.getBirthday()

        s2.setSname("多利");
        System.out.println(s2);
        System.out.println(s2.getSname());
        System.out.println(s2.getBirthday());
    }
}

控制檯輸出：s1修改時間後，s2還是最初的(Sun Feb 08 21:55:32 CST 1970)

com.test.prototype.Sheep2@1db9742
少利
Sun Feb 08 21:55:32 CST 1970
Fri Dec 10 00:59:15 CST 12500
com.test.prototype.Sheep2@647e05
多利
Sun Feb 08 21:55:32 CST 1970

二、S03E234_01【GOF23設計模式】_原型模式、反序列化實現深複製、效率對比、創建型模式總結
利用序列化和反序列化技術實現深複製

package com.test.prototype;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Date;
/**
 * 原型模式(使用序列化和反序列化的方式實現深複製)
 */
public class Client3 {
    public static void main(String[] args) throws Exception {
        Date date = new Date(3333332323L);
        Sheep s1 = new Sheep("少利", date);

        System.out.println(s1);
        System.out.println(s1.getSname());
        System.out.println(s1.getBirthday());

//      Sheep s2 = (Sheep) s1.clone();
        //使用序列化和反序列化實現深複製
        //序列化
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream    oos = new ObjectOutputStream(bos);
        oos.writeObject(s1);
        byte[] bytes = bos.toByteArray();

        //反序列化
        ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
        ObjectInputStream    ois = new ObjectInputStream(bis);

        Sheep s2 = (Sheep) ois.readObject();//深複製的對象

        System.out.println("修改原型對象的屬性值");
        date.setTime(332324355555555L);
        System.out.println(s1.getBirthday());

        s2.setSname("多利");
        System.out.println(s2);
        System.out.println(s2.getSname());
        System.out.println(s2.getBirthday());
    }
}

短時間大量創建對象時，原型模式和普通new方式效率測試：

package com.test.prototype;
/**
 * 測試普通new方式創建對象和clone方式創建對象的效率差異！
 * 如果需要短時間創建大量對象，並且new的過程比較耗時，則可以考慮使用原型模式！
 */
public class Client4 {

    public static void testNew(int size){
        long start = System.currentTimeMillis();
        for (int i = 0; i < size; i++) {
            Laptop t = new Laptop();
        }
        long end = System.currentTimeMillis();
        System.out.println("new的方式創建耗時：" + (end - start));
    }

    public static void testClone(int size) throws CloneNotSupportedException{
        long start = System.currentTimeMillis();
        Laptop t = new Laptop();
        for (int i = 0; i < size; i++) {
            Laptop temp = (Laptop) t.clone();
        }
        long end = System.currentTimeMillis();
        System.out.println("clone的方式創建耗時：" + (end - start));
    }

    public static void main(String[] args) throws Exception {
        testNew(1000);
        testClone(1000);
    }
}

class Laptop implements Cloneable{//筆記本電腦
    public Laptop(){
        try{
            Thread.sleep(10);//模擬創建對象耗時的過程！
        }catch(InterruptedException e){
            e.printStackTrace();
        }
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object obj = super.clone();//直接調用object對象的clone()方法
        return obj;
    }
}

控制檯輸出：

new的方式創建耗時：10168
clone的方式創建耗時：10

開發中的應用場景：
原型模式很少單獨出現，一般和工廠模式一起出現，通過clone的方法創建一個對象，然後由工廠方法提供給調用者。
spring中bean的創建實際就是兩種：單例模式和原型模式（原型模式需要和工廠模式搭配起來）。

創建型模式的總結：