The association with the "space bar" should only apply when a button has
focus.  Pressing the space bar when some other component holds focus
won't invoke your button.

I believe your second item can be resolved by setting a button as
default.  Every JFrame, JDialog, etc., has a JRootPane.  You can then
call that item's getRootPane() method to retrieve it, and then call its
setDefaultButton(JButton) method.  That causes the button to take on a
special appearance, and to respond automatically to pressing
Enter/Return while the dialog has focus.

= Steve =