how can I detect arrow keys in java?

I would recommend using:

if (event.getKeyCode() == KeyEvent.VK_UP) {
...
}

repeating with VK_DOWN, VK_LEFT, VK_RIGHT.

There are seperate codes for the numeric keypad: VK_KP_UP, VK_KP_DOWN, VK_KP_LEFT, VK_KP_RIGHT if you need them.

See KeyEvent for all of the codes.

KeyEvent.VK_LEFT, KeyEvent.VK_RIGHT, etc.

Also, you should use getKeyCode, not getKeyChar. getKeyChar is for keys that actually correspond to characters (letters, numbers, spaces, etc.).

Use

if ( e.getKeyCode() == KeyEvent.VK_LEFT){
     //Do something
}

The other keys are:

KeyEvent.VK_UP

KeyEvent.VK_RIGHT

KeyEvent.VK_DOWN