单例设计模式之枚举实现

public class Singleton {
    private Singleton() {
    }
    private enum EnumHolder {
        INSTANCE;
        private Singleton singleton;
        private EnumHolder() {
            this.singleton = new Singleton();
        }
        public Singleton getSingleton() {
            return singleton;
        }
    }
    public static Singleton getInstance() {
        return EnumHolder.INSTANCE.getSingleton();
    }
}