Double Buffering a JFrame - swing

Question

[Warning, I am a beginner, I have little knowledge about JFrame and I am just getting started, but your help would be greatly appreciated!]
So, here is my Problem: I am currently working on something extremely simple, just a red rectangle moving across the screen and I know how beginner-like that must sound.
My current Code:
package movement;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JFrame;
public class Movement extends JFrame {
public static void main(String[] args) {
Movement m = new Movement();
m.setSize(1000, 1000);
m.setTitle("Movement");
m.setBackground(Color.WHITE);
m.setVisible(true);
m.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void paint (Graphics g){
int width = 0;
int height = 0;
int x = 100;
int y = 900;
while(x < 1000 && y > 0){
//System.out.println("Success");
g.setColor(Color.RED);
g.fillRect(x+width, y-height, 200, 200);
//g.fillRect(x+width, y-height, 200, 200);
try{
Thread.sleep(10);
} catch(InterruptedException e){
}
g.setColor(Color.WHITE);
g.fillRect(x+width, y-height, 200, 200);
//g.fillRect(x+width, y-height, 200, 200);
width=width+1;
height=height+1;
}
}
}
So as you can see it works, but the image stutters and flicks a bit, since there is only a single Buffer. I heard that adding a JPanel would allow me to double buffer and have a way smoother experience, but since I am a real beginner I wouldn't know how to implement it here. I am not sure how a JPanel would help here and in which way to use it.

Answer 1

Swing is double buffered by default. You are overriding the paint() method of the frame and have not invoked super.paint(...) so you are losing the default double buffering.
I heard that adding a JPanel would allow me to double buffer and have a way smoother experience
Yes, this is the proper way to do custom painting. It is not difficult all you do is override the paintComponent() method of the JPanel and add the panel to the frame. Read the section from the Swing tutorial on Custom Painting for more information and examples.
Also, you should NEVER have a while loop with a Thread.sleep() in a painting method. To do animation you should use a Swing Timer. The tutorial link I provided above also has a section on Timers or you can search the forum/web for examples.