1、静态内部类实现单例

package com.caiya.test.singleton;

import org.apache.http.util.Asserts;

/**
 * Created by caiya on 16/10/9.
 */
public class Singleton {

    private String name;

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    private Singleton(){
        System.out.println("init...");
    }

    private static class Holder{
        private static Singleton instance =  new Singleton();
    }

    public static Singleton getInstance(){
        return Holder.instance;
    }

    public static void main(String[] args) {
        Singleton instance1 = Singleton.getInstance();
        instance1.setName("test");
        Singleton instance2 = Singleton.getInstance();
        Asserts.notNull(instance1, "instance1");
        Asserts.notNull(instance2, "instance2");
        Asserts.check(instance1 == instance2, "instance1 != instance2");
        System.out.println(instance2.getName());
    }

}