package com.atguigu.java1;/*** 使用同步机制将单例模式中的懒汉式改写为线程安全的** @author shkstart* @create 2019-02-15 下午 2:50*/
public class BankTest {}class Bank{private Bank(){}private static Bank instance = null;public static Bank getInstance(){//方式一：效率稍差
//        synchronized (Bank.class) {
//            if(instance == null){
//
//                instance = new Bank();
//            }
//            return instance;
//        }//方式二：效率更高if(instance == null){synchronized (Bank.class) {if(instance == null){instance = new Bank();}}}return instance;}}