Getting a 4-digit number from a keypad

Projects Programming
8

but in the sentence: if(keypad.getKey()!= NO_KEY) , I have the "!=" that means different (not equal), so has to wait till the pressing shows a key pressed. I'm right?

No, it does not wait.

This waits:

while(key = keyPad.getKey() == NO_KEY)
{
    // Do nothing
}
// Use key

But, you do NOT want to wait. You want to deal with events when they happen. You do not want to wait for them to happen.