Layout of Swing program question

[Timmy Ryan]

Hi Guys,

This is a cut down program that randomly draws 50 * around the screen and makes them move around.
The code does what I want but if anybody has any suggestions on how the code could be structured better it would be much appreciated.
As in when I improve on the program and want to get the objects to interact with each other should i put the code for that in the paintMethod().

   
import javax.swing.SwingUtilities;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.BorderFactory;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.util.Random;
import java.awt.Point;
import java.util.ArrayList;
import java.math.BigDecimal;
 
public class BasicSwingOne {
   
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {public void run() {createAndShowGUI(); }});
    }
 
    private static void createAndShowGUI() {
        JFrame f = new JFrame("Paint Demo");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        f.add(new MyPanel());
        f.pack();
        f.setVisible(true);
    }
}
 
class MyPanel extends JPanel {
ArrayList<Point> points = new ArrayList<Point>();
 
    public MyPanel() {
for (int i=0; i < 50; i++) {
points.add(new Point(new Random().nextInt(250)+50,new Random().nextInt(250)));
}
    }
 
    public Dimension getPreferredSize() {
        return new Dimension(500,600);
    }
 
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
paintMethod(g);
}
 
public void paintMethod(Graphics g) {
try {
this.repaint();
Thread.sleep(200);
} catch (Exception e) {}
for(Point x: points) {
g.drawString("*",(int)x.getX(),(int)x.getY());
int tempX = (int)x.getX()+ranNum(10);
if (tempX < 50) {
tempX = (int)x.getX();
}
x.setLocation(tempX,(int)x.getY()+ranNum(10));
}
}
 
public int ranNum(int highNumber) {
int temp = new Random().nextInt(highNumber);
if (new Random().nextInt(2) == 0) {
temp = temp  * -1;
}
return temp;
}
}

[Craig Wood]

Things work better if you separate your drawing code from your event code.

import java.awt.*;
import java.util.*;
import java.util.List;
import javax.swing.*;
 
public class BSO {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() { createAndShowGUI(); }
        });
    }
 
    private static void createAndShowGUI() {
        JFrame f = new JFrame("Paint Demo");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
        f.add(new MyPanel());
        f.pack();
        f.setVisible(true);
    }
}
 
class MyPanel extends JPanel implements Runnable {
    List<Point> points = new ArrayList<Point>();
    Random seed = new Random();
 
    public MyPanel() {
        for (int i=0; i < 50; i++) {
            points.add(new Point(seed.nextInt(250)+50,
                                 seed.nextInt(250)));
        }
        Thread thread = new Thread(this);
        thread.setPriority(Thread.NORM_PRIORITY);
        thread.start();
    }
 
    public Dimension getPreferredSize() {
        return new Dimension(500,600);
    }
 
    /** drawing code */
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        for(Point x: points) {
            g.drawString("*", x.x, x.y);
        }
    }
 
    /** event code */
    public void run() {
        while(true) {
            try {
                Thread.sleep(200);
            } catch (Exception e) { break; }
            for(int j = 0; j < points.size(); j++) {
                Point p = points.get(j);
                int tempX = p.x + ranNum(10);
                if (tempX < 50) {
                    tempX = p.x;
                }
                p.setLocation(tempX, p.y+ranNum(10));
            }
            this.repaint();
        }
    }
 
    public int ranNum(int highNumber) {
        int temp = seed.nextInt(highNumber);
        if (seed.nextInt(2) == 0) {
            temp = temp  * -1;
        }
        return temp;
    }
}