A Free game in Java

I wanted to play this game so badly as I use to be very good at it. I was not knowing the proper keyword to find it online. So, what the heck, I went ahead and created one! The front end used was Swing.
The objective of this game is to arrange from numbers 1 through 24 (or depending on the size) in proper order and you have one square free. You can move to that empty sqaure by pressing either of the four arrow keys UP/DOWN/LEFT/RIGHT. All the puzzles formed will have a solution. You can use this code anywhere you want.

If you have Java installed in your browser, you should be able to see the Applet. Just click anywhere inside the applet and start playing using the arrow keys! Have fun!

Screenshot	Applet

	package boxgame;
	import java.awt.*;
	import java.awt.event.KeyEvent;
	import java.util.ArrayList;
	import java.util.List;
	import javax.swing.*;
	public class BoxPuzzle extends JFrame{
	private static final long serialVersionUID = 1L;
	private static final int SIZE = 5;
	JPanel[][] panelArray = new JPanel[SIZE][SIZE];
	private boolean dialogShown = false;
	public BoxPuzzle(){
	this.setTitle(SIZE*SIZE-1+" square puzzle");
	this.add(getGamePanel(SIZE));
	this.setSize(SIZE*75, SIZE*75);
	this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	this.setLocationRelativeTo(null);
	for(int i=0;i<SIZE*100;i++)//RANDOMIZE MOVES
	handleKeyPress((int)(Math.random()*4) + 37);
	processKeys();
	this.setVisible(true);
	}
	private void processKeys(){
	KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(
	new KeyEventDispatcher() {
	public boolean dispatchKeyEvent(KeyEvent e){
	if(e.getID() == KeyEvent.KEY_PRESSED){
	handleKeyPress(e.getKeyCode());
	if(areThingsInPlace() && !dialogShown){
	dialogShown = true;
	JOptionPane.showMessageDialog(null,"Congratulations!!! YOU WIN!!");
	System.exit(1);
	}
	}
	return false;
	}
	});
	}
	private void handleKeyPress(int keyCode) {
	int emptyIndex = findEmptyIndex();
	int x = emptyIndex/SIZE;
	int y = emptyIndex%SIZE;
	switch (keyCode) {
	case 37://LEFT KEY
	if(y==SIZE-1) return;
	doSwap(x,y,x,y+1);
	break;
	case 38://UP KEY
	if(x==SIZE-1) return;
	doSwap(x,y,x+1,y);
	break;
	case 39://RIGHT KEY
	if(y==0) return;
	doSwap(x,y,x,y-1);
	break;
	case 40://DOWN KEY
	if(x==0) return;
	doSwap(x,y,x-1,y);
	break;
	}
	}
	private void doSwap(int x,int y,int x1,int y1){
	Component temp1,temp2;
	temp1 = panelArray[x][y].getComponent(0);
	temp2 = panelArray[x1][y1].getComponent(0);
	panelArray[x][y].remove(0);
	panelArray[x1][y1].remove(0);
	panelArray[x1][y1].add(temp1);
	panelArray[x][y].add(temp2);
	temp2.requestFocus();
	this.repaint();
	}
	private int findEmptyIndex() {
	for(int i=0;i<SIZE;i++)
	for (int j=0;j<SIZE;j++)
	if(!(panelArray[i][j].getComponent(0) instanceof JButton))
	return i*SIZE + j;
	return 0;
	}
	private boolean areThingsInPlace(){
	for(int i=0;i<SIZE*SIZE-1;i++){
	String name = (panelArray[i/SIZE][i%SIZE].getComponent(0)).getName();
	if(name!=null && !(name.equals(""+i)))
	return false;
	}
	return true;
	}
	public static void main(String args[]){
	new BoxPuzzle();
	}
	private JPanel getGamePanel(int difficulty) {
	JPanel pnlGame = new JPanel();
	GridLayout matrixLayout = new GridLayout(difficulty, difficulty);
	pnlGame.setLayout(matrixLayout);
	List<JComponent> componentsList = getRandomizedList(difficulty);
	int index = 0;
	for(int i=0;i<difficulty;i++){
	panelArray[i] = new JPanel[difficulty];
	for(int j=0;j<difficulty;j++){
	panelArray[i][j] = new JPanel();
	panelArray[i][j].setLayout(new GridLayout(1,1));
	panelArray[i][j].add(componentsList.get(index++));
	pnlGame.add(panelArray[i][j]);
	}
	}
	return pnlGame;
	}
	private List<JComponent> getRandomizedList(int difficulty) {
	List<JComponent> componentSet = new ArrayList<JComponent>();
	for(int i=0;i<difficulty*difficulty-1;i++){
	JButton button = new JButton(""+(i+1));
	button.setName(""+i);
	componentSet.add(button);
	}
	componentSet.add(new JPanel());
	return componentSet;
	}
	}

view raw BoxPuzzle.java hosted with ❤ by GitHub

Cheers,
Bragaadeesh.