Question

I would like to do the following (which doesn’t work, it is just to explain the concept). Any idea how to do it?

Class type;
if (/* something */)
  type = String.class;
else
  type = Boolean.class;

return new ArrayList<type>();

ArrayList<type> doesn’t work. I tried with type.getClass(), doesn’t work either.

Answer 1

Wrap it into the method, pass the type as generic Class and let Java do the rest for you. No need for any conditional branching.

<T> List<T> newList(Class<T> type) {
    return new ArrayList<T>();
}

Then you can use it like this:

List<String> list = newList(String.class);

Bear in mind that T does not have to be specified at the generic class level. You can specify generic type for the method and therefore make it a generic method as in the example code.