完美單例模式

單例模式的各種概念網(wǎng)上有很多,這里直接貼代碼:

//classholder
public class Singleton {
        private Singleton(){}
        private static class SingletonHolder(){
                private static final Singleton INSTANCE = new Singleton();
        }
        public static final Singleton getInstance(){
                return SingletonHolder.INSTANCE;
        }
}