java – 为什么我出乎意料地能够创建我的单例类的多个实例？

以下代码成功运行,没有任何错误/异常.

我希望代码失败,因为SingletonExample类有一个私有的默认构造函数.

public class SingletonExample {
    private static SingletonExample singletonInstance;

    private SingletonExample() {
    }

    public static SingletonExample getSingletonInstance() {
        if (null == singletonInstance) {
            System.out.println("Creating new instance");
            singletonInstance = new SingletonExample();
        }
        return singletonInstance;
    }

    public void printSingleton(){
        System.out.println("Inside print Singleton");
    }

    public static void main(String a[])  {
        SingletonExample singObj1 = new SingletonExample();
        SingletonExample singObj2 = new SingletonExample();
    }
}

我的代码有问题吗？