Question

Is there a way to define a type for a Collection?

If I have the following:

private Map<String, A> myMap;

then is there a way to define Map<String, A> as a new type MapOfTypeA, for example, so that I can define myMap as

private MapOfTypeA myMap;

as an extension of this, is there a way to have the following:

myMap = new MapOfTypeA();

actually be

myMap = new HashMap<String, A>();

I’m not sure of what to call what I am asking, but I think I have explained it. In C or C++ it would be a typedef, I think.

Answer 1

You could define MapOfTypeA as

class MapOfTypeA extends HashMap<String, A> {
}

But not sure what the purpose is. If your concern is verbosity, then Java 7 has introduced the diamond operator that you can use to declare your map like this:

Map<String, A> myMap = new HashMap<> ();

instead of

Map<String, A> myMap = new HashMap<String, A> ();