volatile 实现 单例模式
单例模式的一种实现方式,但很多人会忽略volatile关键字,因为没有该关键字,程序也可以很好的运行,只不过代码的稳定性总不是100%,说不定在未来的某个时刻,隐藏的bug就出来了。
双重校验锁
class Singleton { private volatile static Singleton instance;
private Singleton (){} public static Singleton getInstance() { if (instance == null) { syschronized(Singleton.class) { if (instance == null) { instance = new Singleton(); } } } return instance; } }
懒加载的优雅写法静态内部类
public class Singleton {
private Singleton (){}
public static Singleton getInstance(){ return SingletonHolder.instance; }
static class SingletonHolder { static Singleton instance = new Singleton(); }
}
转http://www.jianshu.com/p/195ae7c77afe
http://cantellow.iteye.com/blog/838473