add "public boolean String.contains(char c)"
Java 5.0 finally added String.contains(CharSequence s) - that's good, using String.indexOf(String s)>-1 can get pretty annoying. But this (String.indexOf(char c)>-1) still needs to be done for chars (or the char converted to a CharSequence, e.g. String).
An alternative is to make Character implement the CharSequence interface. Sure, there is no real use for calling .charAt, .length or .subSequence on a Character, but that way and together with the autoboxing chars could be passed as parameters where CharSequences are required - e.g. to the String.contains method. It might not be very efficient, though (autoboxing, then searching the String for a CharSequence, instead of just implementing the method as "return indexOf(c)>-1;").
On the other hand, the String.indexOf methods only allow chars and Strings as parameters. Maybe they should allow CharSequences, too.