FULL PRODUCT VERSION :
Documented in Java SE 1.5.0.09 and Java SE build 1.7.0-ea-b02

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

EXTRA RELEVANT SYSTEM CONFIGURATION :
Verified on two Tablet PC (Motion Computing LS800 and Motion Computing M1300) running Windows XP Tablet PC Edition 2005.

A DESCRIPTION OF THE PROBLEM :
On a Tablet PC, using pen input to click a Checkbox gives two Item Events.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Use a real Tablet PC running Windows XP Tablet PC Edition 2005.
2. Run the applet on www.segal.org/java/just_checkbox/ (code given below) using Firefox or Internet Explorer running the Sun JVM.
3. Open the Sun Java Console.
3. Click the checkbox using the tablet's pen.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Single clicks should produce only one item event.
ACTUAL -
Single clicks typically result in two item events (for some clicks just one).

Details of additional testing:

1. The problem does not occur in the Microsoft JVM.
2. The problem does not occur when using a mouse on a Tablet PC.
3. This problem is particularly troublesome because programmers on non-pen-based computers will not know it is an issue, and a second click on a Checkbox often reverses the effect of the first click.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class just_checkbox extends Applet implements ItemListener {

Checkbox checkbox;
int counter;

public void init()
{
    checkbox = new Checkbox("Checkbox");
    checkbox.addItemListener(this);
    add(checkbox);
}

public void itemStateChanged(ItemEvent ie)
{
    if (ie.getSource() == checkbox) System.out.println("Item event " + ++counter);
}
} // END OF Class just_checkbox
---------- END SOURCE ----------