public enum Singleton {
    INSTANCE;

    private SingletonClass instance;

    Singleton() {
        this.instance = new SingletonClass();
        System.out.println("列舉類建構函式");
    }

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

}

class SingletonClass {
    int i = 0
 
;
    public SingletonClass() {
        System.out.println("SingletonClass被初始化 " + ++i + " 次");
    }
}

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