reference of class!

[ashok khetan]

Read the following piece of code carefully.

public class A
{
A()
{
}
}
1) The class A can be referenced outside the package in which it is defined.
2) The class A cannot be instantiated outside the package in which it is defined.
3) The class A cannot be extended outside the package in which it is defined.
4) The class A can be referenced, instantiated or extended anywhere.
5) The above code will cause a compiler error. The constructors of public class have to be public.
Answer:1,2,3.
can u pl explain what does the option 1) mean?(if possible then with some code)

[Jose Botella]

package other;
public class A {  A(){} }
import other.A;
public class Test {
Test() {System.out.println(new A());}
}

As A() is default access can not be extended or accessed in a different package

[Bindesh Vijayan]

This is what it means:


package p1;
public class A(){
A(){}//default constr. with default access
/*public member */
public static void prt(){
System.out.println("A.prt()");
}
}

outside package p1
import p1;
public class SomeClass{
public static void main(String[] arg){
{
//A a1=new A();//cannot instantiate since constructor of A()has default acces
A.prt();//no problem here, you can refer its public members
}
}


THANKS
[This message has been edited by Bindesh Vijayan (edited September 09, 2001).]

[Muhammad Farooq]

Can somebody tell me why option 3 is correct.
Thanks
--Farooq

[Jose Botella]

Because the default access of the constructor doesn't allow to call it outside the package where it was declared

[Muhammad Farooq]

Thanks Jose,
Does it mean that the public class can be referenced but can not be extended outside its package if the constructor is not public.
--Farooq

[Roopa Bagur]

Thats right because default access has only package accessibility.

Originally posted by Muhammad Farooq:
Thanks Jose,
Does it mean that the public class can be referenced but can not be extended outside its package if the constructor is not public.
--Farooq