Question

Inside of class ATester
{
   private A<Integer> p1,p2;

    p1 = new B<Integer>();
    p2 = new B<Integer>( p1);

}

public class B<E extends Comparable<? super E>> implements A<E>
{
     public B()   // default constructor
     {
        // skip
     }

     public B(B other)  // copy constructor
     {
        // skip
     }

}

I want to define a copy constructor, which takes another B as argument
but when I pass p1 into

p2 = new B<Integer>( p1);

when compile, it gives me error message

“no suitable constructor found for B< A < Integer > >”

What should I change or add?

Answer 1

Change it to

Or call as p2 = new B<Integer>( (B<Integer>)p1);

Because what you are trying to do is send A<Integer> to B in the constructor.
Ultimately it is

B b = element of type A<Integer>

Which is wrong due to contra-variance of argument type. Either change the argument type in you B constructor as per design or do the above mentioned