What is the fastest way to draw pixels in Java

Question

I have some code that generates particles at random locations, and moving in random directions and speed.

Each iteration through a loop, I move all the particles, an

Answer 1

Never call repaint(); that's for noobs, play around with this where you don't have to call repaint();. That method has caused me so much pain and discomfort in the last 2 months, and I am sad nobody told me there is another way. 1,000,000 particles will get expensive real fast, so you may want to consider a Monte Carlo method, see http://raytracey.blogspot.com/ for cheaper rendering options. I don't know if you can afford manipulation of all of these particles while adhering to 20-30fps, I just watched a 10 second fluid simulation that took 3 weeks on a 2.4ghz 6gb ram machine. I apolagise because my only experience in the BufferedImage is importing .png's to draw with Graphics g. I worked on a project that was very computationally expensive very recently and with the timeline I was not able to gpu accelerate my program, so if you're in the same boat, try this package pet;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.io.IOException;
import javax.swing.*;


public class pet extends JPanel implements MouseListener{
public static JFrame frame = new JFrame("frame");
public pet() throws IOException{
 setPreferredSize(new Dimension(870, 675));         //configuring panel
 addMouseListener(this);
}
public static void main(String[] args) throws IOException{
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    JComponent newContentPane = new pet();
    newContentPane.setOpaque(true);
    frame.setContentPane(newContentPane);
    frame.pack();
    frame.setVisible(true);
    frame.addMouseListener(new pet());
}
public void paintRectangleAtPoint(Graphics g, int x, int y){
g.setColor(Color.BLACK);
g.drawRect(x, y, 100,100);
}
public void paintStuff(Graphics g, int x, int y){
g.setColor(Color.BLACK);
g.drawRect(x, y, 100,100);
}
@Override
public void mouseClicked(MouseEvent e) {
paintStuff(frame.getGraphics(),e.getX(), e.getY());

}
@Override
public void mousePressed(MouseEvent e) {
// TODO Auto-generated method stub

}
@Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub

}
@Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub

}
@Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub

}
}