FULL PRODUCT VERSION :
java version "1.6.0_06"
Java(TM) SE Runtime Environment (build 1.6.0_06-b02)
Java HotSpot(TM) Client VM (build 10.0-b22, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows XP Pro SP 2

A DESCRIPTION OF THE PROBLEM :
This is a repeat of 6596142, which is open, and 6525292, where it was declared a feature.

I'm adding a new report because this is a SAFETY HAZARD in our console application.

On an OK/Cancel dialog, the user can use the Tab key to change the focus to Cancel. Pressing Enter returns OK. Pressing the space bar or clicking Cancel returns Cancel.



STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
This is apparently a feature. See source code.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Tab to Cancel, press Enter, get Cancel
ACTUAL -
Tab to Cancel, press Enter, get OK

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package bugs;

import javax.swing.JOptionPane;

public class WrongButton {
/**
* @param args
*/
public static void main(final String[] args) {
final WrongButton instance = new WrongButton();
instance.run();
}

private void run() {
String response = null;
int selectedButton = 0;
while (true) {
selectedButton = JOptionPane.showConfirmDialog(null,
"Click Cancel, get Cancel."
+ "\n"
+ "Press Tab (focus on Cancel), Press Enter, get OK."
+ "\n"
+ "Press Tab (focus on Cancel), Press Spacebar, get Cancel(!).",
"Which Button?",
JOptionPane.OK_CANCEL_OPTION);
if (selectedButton == JOptionPane.OK_OPTION) {
response = "OK selected.";
}
else if (selectedButton == JOptionPane.CANCEL_OPTION) {
response = "Cancel selected.";
}
else {
return;
}
JOptionPane.showMessageDialog(null,
response,
"Selected Button",
JOptionPane.PLAIN_MESSAGE);
}
}
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
I'm considering creating my own confirmation dialog. We use this to query the operator about things like, "This will turn on High Voltage!", seriously. Our customers can't be expected to train every single operator to never make this mistake.

I've never heard of a "default button" on a dialog anyway, except maybe the button that gets the focus by default. After that, the button with the focus is the default. In general, a default button should be selected only when no other button has the focus.