Java

boolean isIdentity(int[][] m) {
 boolean isIdentity = true;
 for(int i = 0; i < m.length; i++) for(j = 0; j < m[i].length; j++)
  isIdentity &= m[i][j] == (i == j ? 1 : 0);
 return isIdentity;
}

1. Please fix your formatting.
2. Which line has the error?
3. What error?

import javax.swing.*;
class CatchTheRat extends JFrame {
	// The Rat
	JLabel lb;

	// Move it randomly!
	Random r;

	public CatchTheRat(int k) {
		createGUI(k);
	}

	private void createGUI(int k) {

		// Set frame properties
		setTitle("Catch The Rat");
		setLayout(new FlowLayout());
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		
//		setExtendedState(MAXIMIZED_BOTH);
		setSize(new Dimension(800,600));
		this.add(createContent(k));
		
		// Maximize the frame
		setVisible(true);
	}

	private JPanel createContent(int k) {
		JPanel oPanel = new JPanel();
		// Set the background (just for a good look)
//		setContentPane(new JLabel(new ImageIcon("background.jpg")));

		// Set layout to the content pane
//		oPanel.setLayout(new FlowLayout());

		// Create the rat
		lb = new JLabel(new ImageIcon("rat.jpg"));

		// Add the rat
		oPanel.add(lb);

		// Create Random object
		r = new Random();

// The random positions do not work, will "hide" the icon therefor

//		// Create a timer and call it for every k seconds
//		new Timer(k, new ActionListener() {
//
//			public void actionPerformed(ActionEvent ae) {
//
//				// Move the rat randomly, subtract 75, so that the rat should
//				// not meet the edges
//				lb.setLocation(r.nextInt(getWidth()), r.nextInt(getHeight()));
//
//			}
//
//		}).start();

		// Add mouselistener, notify when user clicks it!
		lb.addMouseListener(new MouseAdapter() {

			public void mouseClicked(MouseEvent me) {
				// Create a beep sound when clicked to notify
				Toolkit.getDefaultToolkit().beep();

				// Also print it!
				System.out.println("Caught!");
			}

		});
		
		return oPanel;

	}

	public static void main(String args[]) {

		// Create Scanner object
//		Scanner s = new Scanner(System.in);
//
//		// Let the user enter his capability of catching the rat!
//		System.out.println("Enter the speed");
//
//		// Read the input
//		int k = s.nextInt();

		// Create the frame and send the value of k
		new CatchTheRat(5);

	}
}