浅谈设计模式 - 单例模式（一）（下）

/**
 * 静态代码块的形式，实现单例
 *
 * @Author zhaoxudong
 * @Date 2020/10/28 13:28
 **/
public class StaticBlock {
    private static final StaticBlock staticBlock;
    static {
        staticBlock = new StaticBlock();
    }
    public static StaticBlock getInstance() {
        return staticBlock;
    }
}
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package com.zxd.interview.desginpattern.single;
import com.zxd.interview.util.ExecuteUtil;
/**
 * 单例模式 - 静态内部类实现
 *
 * @Author zhaoxudong
 * @Date 2020/10/28 13:35
 **/
public class SingleStaticInner {
    /**
     * 使用内部类来进行后续的构造
     */
    public static class Instatnce {
        private static Instatnce instatnce = new Instatnce();
        public static Instatnce getInstatnce() {
            try {
                // 模拟在创建对象之前做一些准备工作
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return instatnce;
        }
    }
    public static void main(String[] args) throws InterruptedException {
        ExecuteUtil.startTaskAllInOnce(250, new ThreadTest());
    }
}
/**
 * 测试多线程获取对象
 */
class ThreadTest extends Thread {
    @Override
    public void run() {
        System.err.println(SingleStaticInner.Instatnce.getInstatnce());
    }
}
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package com.zxd.interview.desginpattern.single;
import java.io.*;
/**
 * 单例模式 - 序列化与反序列化的问题和解决办法
 * @Author zhaoxudong
 * @Date 2020/10/28 13:55
 **/
public class SingleSerialize {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        SerializeStaticInner instance = SerializeStaticInner.getInstance();
        System.err.println(instance.hashCode());
        // 序列化
        FileOutputStream fileOutputStream = new FileOutputStream("temp");
        ObjectOutputStream objectOutputStream = new ObjectOutputStream(fileOutputStream);
        objectOutputStream.writeObject(instance);
        objectOutputStream.close();
        fileOutputStream.close();
        // 反序列化
        FileInputStream fileInputStream = new FileInputStream("temp");
        ObjectInputStream objectInputStream = new ObjectInputStream(fileInputStream);
        SerializeStaticInner read = (SerializeStaticInner) objectInputStream.readObject();
        objectInputStream.close();
        fileInputStream.close();
        System.err.println(read.hashCode());
    }
    static class SerializeStaticInner implements Serializable{
        private static  SerializeStaticInner serializeStaticInner = new SerializeStaticInner();
        public static SerializeStaticInner getInstance(){
            return serializeStaticInner;
        }
        /**
         * 序列化当中的一个钩子方法
         * 避免序列化和反序列化的对象为新实例破坏单例模式的规则
         */
//        protected Object readResolve(){
//            System.err.println("调用特定的序列化方法");
//            return SerializeStaticInner.serializeStaticInner;
//        }
    }
}
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