Why does Java's TreeSet not specify that its type parameter must extend Comparable?

Posted by Tarski on Stack Overflow See other posts from Stack Overflow or by Tarski
Published on 2010-04-13T19:03:19Z Indexed on 2010/04/13 19:13 UTC
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e.g. The code below throws a ClassCastException when the second Object is added to the TreeSet. Couldn't TreeSet have been written so that the type parameter can only be a Comparable type? i.e. TreeSet would not compile because Object is not Comparable. That way generics actually do their job - of being typesafe.

import java.util.TreeSet;
public class TreeSetTest {
  public static void main(String [] args) {
   TreeSet<Object> t = new TreeSet<Object>();
   t.add(new Object());
   t.add(new Object());
  }
}

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