Java中枚举实现单例模式

	public enum ReYoSingleton {
		INSTANCE;

		private SingletonClass instance;

		ReYoSingleton() {
			this.instance = new SingletonClass();
			System.out.println("枚举类构造函数");
		}

		public SingletonClass getInstance() {
			return this.instance;
		}

	}

	public static class SingletonClass {
		int i = 0;

		public SingletonClass() {
			System.out.println("SingletonClass被初始化 " + ++i + " 次");
		}
	}

	public static void main(String[] args) {
		SingletonClass instance1 = ReYoSingleton.INSTANCE.getInstance();
		SingletonClass instance2 = ReYoSingleton.INSTANCE.getInstance();
		System.out.println("instance1 == instance2: " + (instance1 == instance2));
	}

 运行结果：

当然也可以这样写：

public enum Singleton {

    INSTANCE;

    public void doSomething() {
        System.out.println("doSomething");
    }

}