I've found the following questionable behavior of the
  MenuItem.setLabel method in case of bound arguments 'null' and ""
  (empty string).

  The javadoc for this method claims:
   public void setLabel(String label)
    Sets the label for this menu item to the specified label.
    Parameters:
       label - the new label, or null for no label.

  Under Win32 calling setLabel(null) causes NPE in native code
  (because of null checking in awt_MenuItem.cpp,
  Java_sun_awt_windows_WMenuItemPeer__1setLabel, line 675
  JNI_CHECK_NULL_RETURN(label, "null label").
  Under Solaris, though, it just sets blank label for the menuitem
  which is what it's supposed to do.

  But under Solaris very strange things happen when calling setLabel("") -
  it sets garbage as the label (actually, it somehow recalls the first
  label which has been set for this menu item)
  Under Win32 setting "" as a label just sets blank label which is ok.

  Here is a small test which could help to examine the problem:

import java.awt.*;
import java.awt.event.*;

public class Test {
    Frame frame = new Frame();
    Menu menu = new Menu("Menu");
    MenuItem mi = new MenuItem("Item");
    MenuBar mb = new MenuBar();
    Button button1 = new Button("set to null");
    Button button2 = new Button("set to empty str");
    Button button3 = new Button("set to 'stuff'");

    public Test() {
        button1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                System.err.println("setting the label to null");
                mi.setLabel(null);
            }
        });
        button2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                System.err.println("setting the label to empty");
                mi.setLabel("");
            }
        });
        button3.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ev) {
                System.err.println("setting the label to 'stuff'");
                mi.setLabel("stuff");
            }
        });
        menu.add(mi);
        mb.add(menu);
        frame.add("North", button1);
        frame.add("South", button2);
        frame.add("Center", button3);
        frame.setMenuBar(mb);
        frame.pack();
        frame.setVisible(true);
    }
    public static void main( String[] args ) {
        new Test();
    }
}

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