Why does Java's TreeSet remove(Object) not take an E

Question

From the Java 6 TreeSet Documentation:

boolean remove(Object o):
    Removes the specified element from this set if it is present.

Answer 1

Well, each E is also an Object, and perhaps you have the E not as E at the moment (e.g from an Event source), which makes it convenient for you. Otherwise you just have to cast it to E only to remove it.

From an equality point of view this doesn't matter: The given object's reference address is tested if it equals a set's content, so it doesn't matter of which class it is.