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I have a colored box, I want it to change color every 1/2 second, however I want my code to run as well.

I'm using Java AWT's Graphic Api to draw using g.fillRect(568, 383, 48, 48); where g is wrapped to 'Graphics.'

So you'd think that its simple right?

Color[] colors

colors = new Color[4];

colors[0] = new Color(Color.red);
colors[1] = new Color(Color.blue);
colors[2] = new Color(Color.green);
colors[3] = new Color(Color.yellow);

for(int i = 0; i < colors.length; i++)
 g.setColor(colors[i]);
 g.fillRect(568, 383, 48, 48);

This is all cool but the problem is that none of my program runs when this for loop is running...

I think I can make the game 'Multi-Threaded' which means it can do more than one thing at a time but I have no idea how to do this and it sounds hard, all help appreciated!

Most UI frameworks aren't thread safe, so you need to beware of that. For example, in Swing, you could use a Swing Timer to act as a pseudo loop. Because the Timer notifies the ActionListener from within the context of the Event Dispatching Thread, it makes it safe to update the UI or the state of the UI from within, without risking thread race conditions

Take a look at Concurrency in Swing and How to use Swing Timers for more details

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class JavaApplication430 

 public static void main(String[] args) 
 new JavaApplication430();
 

 public JavaApplication430() 
 EventQueue.invokeLater(new Runnable() 
 @Override
 public void run() UnsupportedLookAndFeelException ex) 
 ex.printStackTrace();
 

 JFrame frame = new JFrame("Testing");
 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 frame.add(new TestPane());
 frame.pack();
 frame.setLocationRelativeTo(null);
 frame.setVisible(true);
 
 );
 

 public class TestPane extends JPanel 

 private Color[] colors;
 private int whichColor = 0;

 public TestPane() 

 colors = new Color[4];

 colors[0] = Color.red;
 colors[1] = Color.blue;
 colors[2] = Color.green;
 colors[3] = Color.yellow;

 Timer timer = new Timer(500, new ActionListener() 
 @Override
 public void actionPerformed(ActionEvent e) 
 whichColor++;
 repaint();
 if (whichColor >= colors.length) 
 whichColor = colors.length - 1;
 ((Timer)(e.getSource())).stop();
 
 
 );
 timer.start();
 

 @Override
 public Dimension getPreferredSize() 
 return new Dimension(200, 200);
 

 @Override
 protected void paintComponent(Graphics g) 
 super.paintComponent(g);
 Graphics2D g2d = (Graphics2D) g.create();
 g2d.setColor(colors[whichColor]);
 g2d.fillRect(0, 0, getWidth(), getHeight());
 g2d.dispose();
 

 

I cannot imagine how you could create an interactive game if your code is single thread. To change the box color periodically you will have to put your thread to sleep. If your game is not multi-thread, then this will freeze your application, preventing user interaction. You will find a lot of interesting materials about programming with threads in Java:

http://docs.oracle.com/javase/tutorial/essential/concurrency/

http://www.ibm.com/developerworks/library/j-thread/

http://moderntone.blogspot.com.br/2013/02/a-simple-java-multithreading-example.html

Just google it!