A DESCRIPTION OF THE REQUEST :
The array initializer syntax allows an optional trailing comma which is ignored. Here is the grammar from JLS:

ArrayInitializer:
{ VariableInitializersopt ,opt }

See bug http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=1204519

Allow similar optional trailing comma in all the places where comma is used as a separator. The places I can think of are:

- implements clause interface list
- throws clause exception list
- method parameters
- method call parameters

I know this is a compatible change to the JLS. However the impact may be relatively small (except for language tools) as the comma is optional and is ignored.

JUSTIFICATION :
This is an ease of use issue for me. I wish I had brought it up during the Tiger days when the ease of use changes were made to the language.

This is useful when quickly reordering items in comma separated lists. I find myself deleting and adding commas when reordering the parameters in a method declaration or method call.

I have seen a lot of special code in many code generation tools when dealing with last and non last or first and non first items in the comma separated list.

I find it easy to work with array initializers due to the support for optional trailing comma.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The optional trailing comma is supported in cases stated in the description and is ignored.
ACTUAL -
The trailing comma is not allowed in case stated in the description.