import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane;

public class Checkerboard extends Frame implements ActionListener
{

    Panel boardPanel = new Panel();
    TextArea numberArea[] = new TextArea[16];
    Panel buttonPanel = new Panel();
    Button goBut = new Button("Go");
    Label startLabel = new Label("Start");
    Label stepLabel = new Label("Step");
    Label stopLabel = new Label("Stop");
    Panel inputPanel = new Panel();
    int start=0, stop=0, step=0;
    TextField startField = new TextField();
    TextField stepField = new TextField();
    TextField stopField = new TextField();


    public Checkerboard()
    {
        // set layouts for frame and two panels
        this.setLayout(new BorderLayout());
        boardPanel.setLayout(new GridLayout(4,4));
        inputPanel.setLayout(new GridLayout(2,3));
        buttonPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

        // add components to board Panel
        for (int i = 0; i < numberArea.length; i++) {
            numberArea[i] = new TextArea(null, 3, 5, 3);
            numberArea[i].setText(Integer.toString(i));
            numberArea[i].setEditable(false);
            numberArea[i].setBackground(Color.WHITE);
            boardPanel.add(numberArea[i]);
        }

        // add components to input Panel
        inputPanel.add(startField);
        inputPanel.add(stepField);
        inputPanel.add(stopField);
        inputPanel.add(startLabel);
        inputPanel.add(stepLabel);
        inputPanel.add(stopLabel);

        //buttonPanel Component
        buttonPanel.add(goBut);

        // add panels to frame
        add(boardPanel, BorderLayout.NORTH);
        add(inputPanel, BorderLayout.CENTER);
        add(buttonPanel, BorderLayout.SOUTH);

        goBut.addActionListener(this);

        // overriding the windowClosing() method will allow the user to click the Close button
        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });

    }// end of constructor method

    public static void main(String[] args) {
        Checkerboard f = new Checkerboard();
        f.setBounds(50, 100, 300, 400);
        f.setTitle("Checkerboard Array");
        f.setVisible(true);
    }// end of main() method

    public void actionPerformed(ActionEvent e)
    {
        try
        {
            start = Integer.parseInt(startField.getText());
            step = Integer.parseInt(stepField.getText());
            stop = Integer.parseInt(stopField.getText());

        }catch(Exception exception)

        {
            return;
        }

        Object src = e.getSource();

        for (int x = start -1; x < stop; x = step)//you need to do the -1 because the array subscript values in Java all start
        //with zero, but humans use numbers starting with 1
        {
            //numberArea[x] = numberArea[start & start++].setBackground(Color.magenta);//..change the color for that square here

            if (src == goBut)
            {
            if (start >= 0 && start <= 15 && start < stop) {
                numberArea[x] = numberArea[start & start++].setBackground(Color.magenta);

            }
            else
            {
                JOptionPane
                        .showMessageDialog(
                                null,
                                "You have entered an incorrect number or a number larger than 15. Please try again",
                                "Error", JOptionPane.ERROR_MESSAGE);
            }

            if (step >= 0 && step <= 15 && start < stop) {
                numberArea[x] = numberArea[step & step++].setBackground(Color.yellow);
            }
        }
}
    }

    // clears stop, stop, step
    void clearFields() {
        startField.setText("");
        stepField.setText("");
        stopField.setText("");
        startField.requestFocus();
        boardPanel.setBackground(Color.WHITE);
    }// end of clearFields() method

}// end of Checkerboard class