相关疑难解决方法(0)

例如,我有Singleton静态字段的类instance:

public class Singleton {

    private static Singleton instance;

    // other code, construct, getters, no matter    
}

我可以用两个不同的类加载器加载这个类两次.我怎么能避免它？这是不安全和危险的.

另外,如果我将实例设置为null,它是否会为两个类设置为null？

Singleton singleton = Singleton.getInstance();
singleton = null;

我正在研究单身人士,我开发了一个非常基本的单身人士课程.

public class SingletonObject {
    private static SingletonObject ref;
    private SingletonObject () //private constructor
    { }

    public  static synchronized   SingletonObject getSingletonObject()
    {
        if (ref == null)
            ref = new SingletonObject();
                return ref;
        }


    public Object clone() throws CloneNotSupportedException
    {throw new CloneNotSupportedException ();
    }   
}

现在下面是我破解单身人士的一种方式..

public class CrackingSingleton {

     public static void main(String[] args) throws ClassNotFoundException,
       IllegalArgumentException, SecurityException,
       InstantiationException, IllegalAccessException,
       InvocationTargetException {

        //First statement retrieves the Constructor object for private constructor of SimpleSingleton class.
        Constructor pvtConstructor = Class.forName("CrackingSingleton.SingletonObject").getDeclaredConstructors()[0];
        //Since the …