FULL PRODUCT VERSION :
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
Java HotSpot(TM) 64-Bit Server VM (build 1.5.0_06-b05, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux ubuntu 2.6.12-10-amd64-generic #1 Sat Mar 11 16:15:30 UTC 2006 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
There are two JList constructors that don't specify their behaviour when passed a null argument:

public JList(Object[] items);
public JList(Vector items);

For both, I'd expect either an IllegalArgumentException or a new JList with an internal model containing zero items. In fact, you get a new JList with an internal model in a very fragile state (it throws a NullPointerException if you try to work with it).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run this test program:

import javax.swing.JList;

public class JListTest
{
  public static void main(String[] args)
  {
    JList list = new JList((Object[]) null);
    System.out.println("OK so far...");
    System.out.println("Model is not null: " + (list.getModel() != null));
    System.out.println("Item count = " + list.getModel().getSize());
  }
}

ACTUAL -
OK so far...
Model is not null: true
Exception in thread "main" java.lang.NullPointerException
at javax.swing.JList$1.getSize(JList.java:315)
at JListTest.main(JListTest.java:10)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.JList;

public class JListTest
{
  public static void main(String[] args)
  {
    JList list = new JList((Object[]) null);
    System.out.println("OK so far...");
    System.out.println("Model is not null: " + (list.getModel() != null));
    System.out.println("Item count = " + list.getModel().getSize());
  }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Developers can just use the JList(ListModel) constructor. Those (like me) working on an alternative implementation of the specification (GNU Classpath, in my case) have to (a) wait for a clarification of the spec / expected behaviour, and (b) implement something now (I'll probably opt for the IllegalArgumentException).