The only problem with the code that you posted is a syntax error. Otherwise it is working. CTRL_DOWN_MASK is a constant in the KeyEvent class so you need to state that:
KeyEvent.CTRL_DOWN_MASK
So the line should be:
it1.setAccelerator(KeyStroke.getKeyStroke('N', KeyEvent.CTRL_DOWN_MASK));
And remove the static import line from your code. That should compile and work as expected.