The following mnemonics which are defined in BasicLookAndFeel.java
can't be changed in basic .properties files.
     "ColorChooser.rgbRedMnemonic", new Integer(KeyEvent.VK_D),
     "ColorChooser.rgbGreenMnemonic", new Integer(KeyEvent.VK_N),
     "ColorChooser.rgbBlueMnemonic", new Integer(KeyEvent.VK_B),
     "FileChooser.cancelButtonMnemonic", new Integer(KeyEvent.VK_C),
     "FileChooser.saveButtonMnemonic", new Integer(KeyEvent.VK_S),
     "FileChooser.openButtonMnemonic", new Integer(KeyEvent.VK_O),
     "FileChooser.updateButtonMnemonic", new Integer(KeyEvent.VK_U),
     "FileChooser.helpButtonMnemonic", new Integer(KeyEvent.VK_H),
     "FileChooser.directoryOpenButtonMnemonic", new Integer(KeyEvent.VK_O),

This is a big obstacle for localization.