大话设计模式_单例模式
一：单线程
package com.wzs.three;/** * 大话设计模式--page214 单例模式(多线程中,双重锁定) * * @author Administrator * */public class Singleton {private static Singleton instance;private static String lock = "lock";public static Singleton getInstance() {if (null == instance) {synchronized (lock) {if (null == instance) {instance = new Singleton();}}}return instance;}public static void main(String[] args) {Singleton singleton1 = Singleton.getInstance();Singleton singleton2 = Singleton.getInstance();if (singleton1 == singleton2) {System.out.println("两个对象是同一个实例.");}}}