Java does not seem to have key codes for several keys on non-US keyboards. This does not prevent the typed characters from being recognized, but it makes it impossible for the Robot class to simulate pressing these keys.
Examples of missing key codes
On a standard French AZERTY keyboard, 2 keys result in a key code of 0 (unknown key code): The key above the tab which generates the character “²” and the much more important ù% key.
On a German QWERTY keyboard, the ß?\ key and the äÄ,öÖ and üÜ keys are undefined.
You can confirm this using the Java KeyEventDemo:
Use the Alt Numpad input method.