KeyEvent Constants in Java

Question

I came across this code:

    private boolean right = true;
    public void keyPressed(KeyEvent e) {

                    int key = e.getKeyCode();

                    if ((key == KeyEvent.VK_LEFT) && (!right)) {
                        left = true;
                        up = false;
                        down = false;
                    }

    }

From my understanding, the getter method called getKeyCode returns a key in integer form. Does a programmer necessarily have to understand the actual numerical value of KeyEvent.VK_LEFT? Or should I treat it as a black box and not care and worry about how it is implemented and just use it?

Apparently the value associated with VK_LEFT is 37 after looking at the Java API.

_what is this actual integer numerical value associated with VK_LEFT?_ Did you try System.out.println("KeyEvent.VK_LEFT value: " + KeyEvent.VK_LEFT); ???? — Pradeep Simha, Dec 30 '12 at 17:02
Ah, I actually did not think about that! But I check the Java API and it says 37. — Nicholas, Dec 30 '12 at 17:06

score 3 · Accepted Answer · answered Dec 30 '12 at 17:02

3

The point about those constants is that you don't have to know the actual numeric value. You could get it easily with a println but you shouldn't (you're not ensured the value won't change in a future release).

Treat them as black boxes.

answered Dec 30 '12 at 17:02

Denys Séguret

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Thanks I never knew I can treat key constants as a black boxes too. I always thought that was just for methods. – Nicholas Dec 30 '12 at 17:11

score 1 · Answer 2 · answered Dec 30 '12 at 17:06

1

Never worry about associated value for any keys. Just use KeyEvent class static variables.

 public static final int VK_LEFT = 0x25;

answered Dec 30 '12 at 17:06

vels4j

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what is 0x25? a hexadecimal? I checked the Java API and it says the constant is 37. How come you posted 0x25? – Nicholas Dec 30 '12 at 17:12
added link too just click key event. 37 is dec for hex 25 – vels4j Dec 30 '12 at 17:18

KeyEvent Constants in Java

2 Answers2