another java generic question

Question

I have the following class:

interface Able{/* ... */}
class A implements Able{/* ... */}

and I have

Map

        

Answer 1

Collection is the supertype for all kinds of collection. It is not a collection that can hold any type. At least that was my misunderstanding of the whole concept.

We can use it where we don't care about the generic type, like in this example:

public static void print(Collection aCollection) {
  for (Object o:aCollection) {
    System.out.println(o);
  }
}

If we had chosen the signature instead:

public static void print(Collection