Why is my Java Applet flickering?

Question

I am working on a small Java Applet that has 3 balls bounce around on screen. When they collide with the walls they make one sound and when they collide with eachother they make another sound.

My issue is that the balls flicker for some reason and I am not sure why. If someone can explain why they are flickering and how I can go about fixing the issue that would be greatly appreciated.

Here is my code:

import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class ass3 extends Applet implements Runnable {
int[] positionX = {0, 0, 0};
int[] positionY = {0, 0, 0};
int[] incrementX = {3, 7, 4};
int[] incrementY = {8, 4, 5};
Thread t;
AudioClip sound;
AudioClip collide;
public void init(){
    sound = getAudioClip(getDocumentBase(), "Audio1.au");
    collide = getAudioClip(getDocumentBase(), "Audio2.au");
}
public void start() {
    t = new Thread(this);
    t.start();
}
public void paint(Graphics g) {
    g.fillOval(getWidth()-50-positionX[0], getHeight()-50-positionY[0], 50, 50);
    g.fillOval(getWidth()-450-positionX[1], getHeight()-450-positionY[1], 50, 50);
    g.fillOval(getWidth()-450-positionX[2], getHeight()-50-positionY[2], 50, 50);
}
public void run() {
    while (true) {
        try {
        Thread.sleep(30);
        } catch (InterruptedException e) {}
        for (int i=0; i < 3; i++) {
            positionX[i] += incrementX[i];
            positionY[i] += incrementY[i];
        }
        // ball 1
        if (positionX[0] > 500 || positionX[0] < 0) {
            incrementX[0] = -incrementX[0];
            sound.play();
        }
        repaint();
        if (positionY[0] > 500 || positionY[0] < 0) {
            incrementY[0] = -incrementY[0];
            sound.play();
        }
        repaint();
        // ball 2
        if (positionX[1] > 100 || positionX[1] < -400) {
            incrementX[1] = -incrementX[1];
            sound.play();
        }
        repaint();
        if (positionY[1] > 100 || positionY[1] < -400) {
            incrementY[1] = -incrementY[1];
            sound.play();
        }
        repaint();
        // ball 3
        if (positionX[2] > 100 || positionX[2] < -400) {
            incrementX[2] = -incrementX[2];
            sound.play();
        }
        repaint();
        if (positionY[2] > 500 || positionY[2] < 0) {
            incrementY[2] = -incrementY[2];
            sound.play();
        }
        repaint();
        // collision
        if (Math.sqrt(((getWidth()-50-positionX[0])-(getWidth()-450-positionX[1]))*((getWidth()-50-positionX[0])-(getWidth()-450-positionX[1])) + ((getHeight()-50-positionY[0])-(getHeight()-450-positionY[1]))*((getHeight()-50-positionY[0])-(getHeight()-450-positionY[1]))) <= 50) {
            incrementX[0] = -incrementX[0];
            incrementY[0] = -incrementY[0];
            incrementX[1] = -incrementX[1];
            incrementY[1] = -incrementY[1];
            collide.play();
        }
        repaint();
        if (Math.sqrt(((getWidth()-50-positionX[0])-(getWidth()-450-positionX[2]))*((getWidth()-50-positionX[0])-(getWidth()-450-positionX[2])) + ((getHeight()-50-positionY[0])-(getHeight()-50-positionY[2]))*((getHeight()-50-positionY[0])-(getHeight()-50-positionY[2]))) <= 50) {
            incrementX[0] = -incrementX[0];
            incrementY[0] = -incrementY[0];
            incrementX[2] = -incrementX[2];
            incrementY[2] = -incrementY[2];
            collide.play();
        }
        repaint();
        if (Math.sqrt(((getWidth()-450-positionX[2])-(getWidth()-450-positionX[1]))*((getWidth()-450-positionX[2])-(getWidth()-450-positionX[1])) + ((getHeight()-50-positionY[2])-(getHeight()-450-positionY[1]))*((getHeight()-50-positionY[2])-(getHeight()-450-positionY[1]))) <= 50) {
            incrementX[2] = -incrementX[2];
            incrementY[2] = -incrementY[2];
            incrementX[1] = -incrementX[1];
            incrementY[1] = -incrementY[1];
            collide.play();
        }
        repaint();
    }
}

}

Possible duplicate of [How do you double buffer in java for a game?](https://stackoverflow.com/questions/10508042/how-do-you-double-buffer-in-java-for-a-game) — LhasaDad, Mar 28 '18 at 23:57
you might be interested in this: https://stackoverflow.com/questions/10508042/how-do-you-double-buffer-in-java-for-a-game — LhasaDad, Mar 28 '18 at 23:57

score 0 · Answer 1 · answered Mar 28 '18 at 23:58

0

Simple, stop calling repaint multiple times. (You're calling it multiple times in your while loop).

answered Mar 28 '18 at 23:58

Oleg

6,124
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I made it so it only had one repaint but it still flickering. – Connor Smyth Mar 29 '18 at 00:13
@ConnorSmyth Then you have to use double buffering as suggested by Lhasa – Oleg Mar 29 '18 at 00:14

Why is my Java Applet flickering?

1 Answers1