Towers of hanoi Jpanels not displaying during solution

[wassat676]

This is a class assignment for practicing recursion (Towers of Hanoi), I know that the recursive part (solve() method) is correct and I believe the JPanels (disks) are actually moving panel to panel (pegs). However, the screen doesnt seem to want to update and show the disks each time one moves.

import java.awt.*;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;

import javax.swing.*;
import javax.swing.border.LineBorder;


public class TowersOfHanoiGUI extends JFrame {
	private static final long serialVersionUID = 1L;

	//Constructs the new JFrame with a GUI pane and control pane
	TowersOfHanoiGUI() {
		getContentPane().setLayout(new BorderLayout());
		
		add(new GUIPane(), BorderLayout.CENTER);
		add(new GUIControlPane(), BorderLayout.EAST);
		
		
	}
	
	//main method
	public static void main(String[] args) {
		TowersOfHanoiGUI frame = new TowersOfHanoiGUI();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.setSize(800, 400);
		frame.setResizable(false);
		frame.setTitle("Towers of Hanoi");
		frame.setLocationRelativeTo(null);
		frame.setVisible(true);
		
	}
}

//This panel contains 3 peg panels for holdingthe disks as the move
class GUIPane extends JPanel {
	private static final long serialVersionUID = 1L;
	
	private static Peg peg1;
	private static Peg peg2;
	private static Peg peg3;

	GUIPane() {
		setLayout(new GridLayout(1, 3, 0, 0));
		
		peg1 = new Peg();
		peg2 = new Peg();
		peg3 = new Peg();
		
		add(peg1);
		add(peg2);
		add(peg3);
	}
	
	//This is the actual solution code (recursive)
	public static void solve(int n, char fromTower, char toTower, char auxTower) throws InterruptedException {
		//GUIPane.class.wait();
		int delay = 1000; 
		if (n == 1) {// Stopping condition
			 System.out.println("Move disk " + n + " from " + fromTower + " to " + toTower);
			 moveDisks(fromTower, toTower);
			 Thread.sleep(delay);
		 }
		 else {
		      solve(n - 1, fromTower, auxTower, toTower);
		      System.out.println("Move disk " + n + " from " + fromTower + " to " + toTower);
		      moveDisks(fromTower, toTower);
		      Thread.sleep(delay);
		      solve(n - 1, auxTower, toTower, fromTower);
		}
	}
	
	// This method moves the disks from one stack to the other
	public static void moveDisks(char from, char to) throws InterruptedException {
		Disk hold;
		if (from == 'A' && to == 'B') {
			hold = peg1.getStack().pop();
			peg2.getStack().push(hold);
			peg1.drawDisks();
			peg2.drawDisks();
		} else if (from == 'A' && to == 'C') {
			hold = peg1.getStack().pop();
			peg3.getStack().push(hold);
			peg1.drawDisks();
			peg3.drawDisks();
		} else if (from == 'B' && to == 'A') {
			hold = peg2.getStack().pop();
			peg1.getStack().push(hold);
			peg2.drawDisks();
			peg1.drawDisks();
		} else if (from == 'B' && to == 'C') {
			hold = peg2.getStack().pop();
			peg3.getStack().push(hold);
			peg2.drawDisks();
			peg3.drawDisks();
		} else if (from == 'C' && to == 'A') {
			hold = peg3.getStack().pop();
			peg1.getStack().push(hold);
			peg3.drawDisks();
			peg1.drawDisks();
		} else /*if (from == 'C' && to == 'B')*/ {
			hold = peg3.getStack().pop();
			peg2.getStack().push(hold);
			peg3.drawDisks();
			peg2.drawDisks();
		}
	}
	
	public static Peg getPeg(int n) {
		if (n == 1) {
			return peg1;
		}
		else if (n == 2) {
			return peg2;
		}
		else {
			return peg3;
		}
	}
}

/*
 * The peg class hold the disks (also has a peg shape thing in the paintComponent method)
 * Each Peg (3 total) has a Stack object that the disks get pushed or popped onto by
 * moveDisks().
 * 
 */
class Peg extends JPanel {
	private static final long serialVersionUID = 1L;

	private Stack<Disk> tower;
	
	private int centerX;
	
	Peg() {
		setLayout(null);
		
		tower = new Stack<Disk>();
	}
	
	public void paintComponent(Graphics g) {
		Graphics2D g2d = (Graphics2D)g;
		
		g2d.setColor(Color.black);
		g2d.fillRect(0, 0, getWidth(), getHeight());
		
		g2d.setColor(Color.gray);
		g2d.fill3DRect(getWidth() / 2, (3 * getHeight()) / 8, getWidth() / 20, getHeight(), true);
	}
	
	// This drawDisks method loops through each element in the stack and placed the
	// Disks in the correct point on the screen. Note, this may be bugged, but it 
	// should still be displaying the disk somewhere.
	public void drawDisks() {
		centerX = (getWidth() / 2) + 6;
		for (int j = this.tower.size() - 1; j >= 0; j--) {			
			tower.get(j).setBounds((7 * this.tower.get(j).getDiskNum()),
								   GUIPane.getPeg(2).getHeight() - (15 * this.tower.get(j).getDiskNum()),
								   this.tower.get(j).getDiskWidth(),
								   this.tower.get(j).getDiskHeight());
			add(tower.get(j));
			
			
			tower.get(j).repaint();
			tower.get(j).revalidate();
		}
	}
	
	public Stack<Disk> getStack() {
		return tower;
	}
	
	public int getCenterX() {
		return centerX;
	}
}

}

Any help with this issue would be appreciated, I believe the problem lies
in the drawDisks(), moveDisks(), and maybe solve() methods. Ive tried to fix it 1000 ways to no avail. There is a similar thread ill try to find it.

[Fubarable]

too long; didn't read

but I did search for Thread.sleep(...) and found it. Not sure if this is your problem but it could cause problems by putting your whole GUI app to sleep. Consider perhaps a Swing Timer. And you may want to isolate your problem a bit so you could post smaller amount of code.

[wassat676]

Well, its nothing to do with Thread.sleep because I took that out and set the number of disks to 12 (requires 4095 moves to solve) and the thing still doesnt update when a disk is moved.

I also shortened it a bit, took out some code that I dont think really matters, Just know that the Disk object is just a jpanel.

[DarrylBurke]

You're blocking the EDT with program logic and that doesn't allow it to repaint the GUI.
Lesson: Concurrency in Swing (The Java™ Tutorials > Creating a GUI With JFC/Swing)

db