java

/**
* Copyright 2013 - 2019 版权所有
*
* Eamil：[e-mail]
*/
package per.shanpeng.maven;

/**
* @author SHAN PENG
* @date 2019-08-06 22:07
* @version V.0.1
*
*/
public class DoubleCheckSingle {

    private static DoubleCheckSingle instance = null;

    private DoubleCheckSingle(){}

    public static DoubleCheckSingle getInstance() {
        if (instance == null) {
            synchronized (DoubleCheckSingle.class) {
                if (instance == null) {
                    instance = new DoubleCheckSingle();
                }
            }
        }
        return instance;
    }

}




/**
* Copyright 2013 - 2019 版权所有
*
* Eamil：[e-mail]
*/
package per.shanpeng.maven;

/**
* 静态内部类单例【推荐】
* @author SHAN PENG
* @date 2019-08-06 22:03
* @version V.0.1
*
*/
public class StaticInnerSingle {

    private StaticInnerSingle() {}

    /**
     * 获取单例
     * @return
     */
    public static StaticInnerSingle getInstance() {
        return InnerClass.single;
    }

    private static class InnerClass{
        private static StaticInnerSingle single = new StaticInnerSingle();
    }

}


/**
* Copyright 2013 - 2019 版权所有
*
* Eamil：[e-mail]
*/
package per.shanpeng.maven;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

/**
* @author SHAN PENG
* @date 2019-08-06 21:47
* @version V.0.1
*
*/
public class SerializableSingle implements Serializable {

    /** 单例实例 **/
    private static volatile SerializableSingle serializableSingle = null;

    /***
     * 私有化构造器
     */
    private SerializableSingle() {}

    /**
     * 获取单例
     * @return
     */
    public static SerializableSingle getInstatnce() {
        if (serializableSingle == null) {
            synchronized (SerializableSingle.class) {
                if (serializableSingle == null) {
                    serializableSingle = new SerializableSingle();
                }
            }
        }
        return serializableSingle;
    }

    /**
     * 反序列化之后依然是单例
     * @return
     */
    public Object readResolve() {
        return serializableSingle;
    }

    public static void main(String[] args) throws IOException, ClassNotFoundException {
        SerializableSingle single = SerializableSingle.getInstatnce();
        FileOutputStream fos = new FileOutputStream(new File("d:/tmp/test.txt"));
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        oos.writeObject(single);
        oos.close();
        fos.close();
        System.out.println(single.hashCode());
        System.out.println("---------------------------");

        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("d:/tmp/test.txt")));
        SerializableSingle single1 = (SerializableSingle) ois.readObject();
        System.out.println(single1.hashCode() == single.hashCode());
    }

}


/**
* Copyright 2013 - 2019 版权所有
*
* Eamil：[e-mail]
*/
package per.shanpeng.maven;

/**
* @author SHAN PENG
* @date 2019-08-06 21:40
* @version V.0.1
*
*/
public class EnumSingle {

    private EnumSingle () {}

    /**
     * 枚举单例模式
     * 1、序列化安全
     * 2、线程安全
     * @return
     */
    public static EnumSingle getInstance() {
        return  Single.INSTANCE.getInstance();
    }

    private enum Single{

        /** 单例 **/
        INSTANCE;

        private EnumSingle enumSingle;

        Single() {
            enumSingle = new EnumSingle();
        }

        public EnumSingle getInstance() {
            return enumSingle;

        }
    }

}