Double-check idiom for lazy initialization of instance fields

首先这两种方式都是延迟初始化机制,就是当要用到的时候再去初始化. 但是Effective Java书中说过:除非绝对必要,否则就不要这么做. 1. DCL (double checked locking)双重检查: 如果出于性能的考虑而需要对实例域(注意这个属性并没有被static修饰)使用延迟初始化,就使用双重检查模式 public class Singleton { private volatile Singleton uniqueInstance; private Singleton(){

Lazy initialization - It decreases the cost of initializing a class or creating an instance, at the expense of increasing the cost of accessing the lazily initialized field. Depending on what fraction of lazily initialized fields eventually require i

Lazy initialization (also sometimes called lazy instantiation, or lazy loading) is a technique for delaying the creation of an object or some other expensive process until it's needed. When programming for iOS, this is helpful to make sure you utiliz

这两天在看开源项目时,发现Event Bus和Universalimageloader中写单例模式都是Double Check的形式.平时总是看到各种各样的单例模式,如,饿汉式,懒汉式等等.其中大多存在问题.今天记录一种比较优秀的单例模式的写法------Double Check.以后我准备就用这种方法了.(虽然还有其他优秀的方式,比如内部静态类,枚举) 先上代码: public class ImageLoader { private volatile static ImageLoader in

Swift中是存在和OC一样的懒加载机制的,但是这方面国内的资料比较少,今天把搜索引擎换成了Bing后发现用Bing查英文\最新资料要比百度强上不少. 我们在OC中一般是这样实现懒加载初始化的: 1: @property (nonatomic, strong) NSMutableArray *players; 2:   3: - (NSMutableArray *)players { 4: if (!_players) { 5: _players = [[NSMutableArray alloc

ThreadStatic 属性对于字段无效 最近使用RESHARPER,发现有这个提示,查了下资料 Occa­sion­ally you might want to make the value of a sta­tic or instance field local to a thread (i.e. each thread holds an inde­pen­dent copy of the field), what you need in this case, is a thread-lo

话不多说直接上代码: public sealed class Singleton { private static Singleton _instance = null; // Creates an syn object. private static readonly object SynObject = new object(); Singleton() { } public static Singleton Instance { get { // Double-Checked Lockin

[单件类] 保证只能有一个实例化对象,并提供全局的访问入口. [设计注意事项] 1.阻止所有实例化的方法: private 修饰构造函数,赋值构造函数,赋值拷贝函数. 2.定义单实例化对象的方法: a.使用static 修饰 b.使用new+delete的方法 3.多线程版本: 使用双检测锁定,即先检测单实例对象是否存在:不存在,使能"锁",再次判断实例是否存在,不存在就创建该单实例对象. A.单层锁示例: Singleton* Singleton::getInstance() { L

Lazy initialization - It decreases the cost of initializing a class or creating an instance, at the expense of increasing the cost of accessing the lazily initialized field. Depending on what fraction of lazily initialized fields eventually require i