Question

I started playing with someone’s else code and came across an interesting experiment. The program will work fine with the if statement. But I found out if I change the if statement into a while loop, the program runs but I could not close the program with the X button instead I had to press Eclipse terminate button. I am guessing this is a sign of an infinite loop or is it the fact that Java cannot repeatedly draw the same images over and over again?

// if you want to draw graphics on the screen, use the paintComponent method
        // it give you a graphic context to draw on
        public void paintComponent(Graphics g){

            super.paintComponent(g);

            // when the player is still in the game
            if(inGame){
                g.drawImage(apple, apple_x, apple_y, this);

                for (int z = 0; z < dots; z++) {
                    if (z == 0)
                        g.drawImage(head, collisionX[z], collisionY[z], this);
                    else g.drawImage(tail, collisionX[z], collisionY[z], this);
                }
                Toolkit.getDefaultToolkit().sync();

                // dispose graphics and redraw new one
                g.dispose();
            }
            else gameOver(g);
        }

Answer 1

If you want your UI to remain responsive, event handlers and repaints should finish within a reasonable amount of time. This means you shouldn’t loop inside paintComponent() at all; instead you have to repeatedly trigger a repaint from somewhere else, like an animation timer.