accessing protected method in other package?

Question

If I say

class A{
}

then it implicitly inherits Object class.So I am having the class as below:

class A{

       protected Object clone(){
       }  /// Here i am not overridning
       //All the other methods (toString/wait/notify/notifyAll/getClass)
}

Now Why cant I access the clone() method in Class B which is in the same package of class A.

Class B{
       A a = new A();
       a.clone();
       **
}

//** Says clone is protected in Object class . But I am not accessing Object's clone method .Here I am invoking class A's clone method anyway which I havn't overloaded yet.

Answer 1

The protected method is defined in the java.lang.Object, so you can't invoke it from another package - only from subclasses.

You are calling it on a a reference to A but it is a method of java.lang.Object, until you override it.

When overriding clone(), you should change the modifier to public and implement Cloneable. However using the clone() method is not a good idea, because it's very hard to implement it correctly. Use commons-beanutils to make shallow clones.

Make sure you make distinction between "overriding" and "overloading".

Answer 2

this perfectly work

class A{

       protected Object clone(){
           return this;
       }  
}

public class B{
       public B() {
           A a = new A();
           a.clone();
           System.out.println("success");
       }
       public static void main(String[] args) {
        new B();
    }

}

Answer 3

If you don't redefine the clone method for A, then, don't be surprise if you are indeed invoking Object's clone() method and not A's.

You get the very same error with

class A {}

class B {
  A a = new A();

  public B() {
    A x = (A) ((Object) a).clone();
  }
}