Input in Games is handled through a series of events that trigger either mouse, keyboard, etc. input. Often, trying to have multiple states of the game as well as hundreds of sprites all trying to grab input at the same time through meager event handling can be difficult. And how about when more than one key is held down? And how can you make this all take very little time later on? Well, let me introduce you to the InputManager class:

public class InputManager implements KeyListener {
	
	public static boolean leftPressed = false;
	public static boolean rightPressed = false;
	public static boolean upPressed = false;
	public static boolean downPressed = false;
	public static boolean spacePressed = false;

	@Override
	public void keyPressed(KeyEvent e) {
            // Edited this part due to pbl.
            int key = e.getKeyCode();
		if (key == KeyEvent.VK_LEFT)
			leftPressed = true;
		if (key == KeyEvent.VK_RIGHT)
			rightPressed = true;
		if (key == KeyEvent.VK_UP)
			upPressed = true;
		if (key == KeyEvent.VK_DOWN)
			downPressed = true;
		if (key == KeyEvent.VK_SPACE)
			spacePressed = true;
		if (key == KeyEvent.VK_ESCAPE)
			quit.cleanAndQuit();
	}

	@Override
	public void keyReleased(KeyEvent e) {
            // Edited this part due to pbl.
            int key = e.getKeyCode();
		if (key == KeyEvent.VK_LEFT)
			leftPressed = false;
		if (key == KeyEvent.VK_RIGHT)
			rightPressed = false;
		if (key == KeyEvent.VK_UP)
			upPressed = false;
		if (key == KeyEvent.VK_DOWN)
			downPressed = false;
		if (key == KeyEvent.VK_SPACE)
			spacePressed = false;
	}

	@Override
	public void keyTyped(KeyEvent e) {}
}

It's a really simple class that if a key is pressed, it sets a boolean to true, and when released, sets it to false. Additionally, if multiple keys are pressed an/or released, it works well because the program is not caught up in the event handling code. It merely sets a variable and moves on.

Now, in order to activate key handling to this class, set it like this in a constructor of the top-level class (a JPanel or JFrame).

addKeyListener(new InputManager());

Now, all you must do is to write a handleInput() method that updates a sprite's location if a key is pressed.

    public void doInput() {
		
        if (InputManager.rightPressed)
		xSpeed = 5;
	else if (InputManager.leftPressed))
		xSpeed = -5;
	else
		xSpeed = 0;
		
	if (InputManager.upPressed)
		ySpeed = -5;
	else if (InputManager.downPressed)
		ySpeed = 5;
	else 
		ySpeed = 0;
		
	if (InputManager.spacePressed) {
		// Jump...or shoot...or...something.
	}
			
    }

See how simple this is not to implement in real gaming situations? This class could also have private variables and methods if you don't believe in having this much access directly to variables. Additionally, if needed, this class could prove to be a fun Singleton project, but only if you have a need for one.