个人的java面试题库.zip

package com.dcm.d_designPattern.singleton; /** * 双重线程检查模式 * * 优点：延迟加载，线程安全 * 缺点： 写法复杂，不简洁 * @author dcm * */ public class SingletonDouble { private static volatile SingletonDouble sInst = null; // <<< 这里添加了 volatile // 私有的构造函数 private SingletonDouble() {} public static SingletonDouble getInstance() { SingletonDouble inst = sInst; // <<< 在这里创建临时变量 if (inst == null) { synchronized (SingletonDouble.class) { inst = sInst; if (inst == null) { inst = new SingletonDouble(); sInst = inst; } } } return inst; // <<< 注意这里返回的是临时变量 } protected void print() { System.out.println("SingletonDouble"); } // test public static void main(String[] args) { SingletonDouble s = SingletonDouble.getInstance(); s.print(); } }