高并发下的单例模式写法

package com.yxj;

/**
 * @author xinjian
 * @create 2018/12/10
 */
public class Singleton {

    private static Singleton singleton;

    private Singleton(){
    }

    public static Singleton getSingleton(){
        if(singleton == null){
            synchronized (Singleton.class){
                if(singleton == null){
                    singleton = new Singleton();
                }
            }
        }
        return singleton;
    }
}