Why is Java's type inference so weak?

Question

Say, I have a method:

public static  Collection addToCollection(T element, Collection collection) {
    collection.add(element);
          


        

Answer 1

Collections.emptyList() returns a List<Object> which is passed through your addToCollection() method. And since Object is not Integer, this fails.

Answer 2

The type inference system has been improved in Java 8, with the introduction of target typing, in order to give more expressivity to streams and lambdas. As a consequence your code compiles with Java 8.

More about it in the updated tutorial, with a very similar example towards the very bottom of the page.

Answer 3

Whats harm in doing this?

Integer i = 42;
List<Integer> emptyList = Collections.emptyList();
Collection<Integer> result = addToCollection(i, emptyList);

In java 8 it will be taken care.