On KeyEvent x不断增加

Question

当我按下左键时，当我松开按钮时，它会不断增加X

public void keyPressed(KeyEvent e){

    int key = e.getKeyCode();

    if(key==KeyEvent.VK_LEFT) dx += 5;
    if(key==KeyEvent.VK_RIGHT){
        dx += 5;
    }
    if(key==KeyEvent.VK_UP){

        dy += 5 * Math.sin(angle);
    }

}