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

public class myCheckerboard extends Frame implements ActionListener
{
    //declare variables
    int start, stop, step;

    Panel boardPanel = new Panel();
        TextArea boardDisplay[] = new TextArea[16];

    Panel buttonPanel = new Panel();
        Button goButton = new Button("Go");

    Panel inputPanel = new Panel();
        Label startLabel = new Label("Start");
        TextField startField = new TextField(2);
        Label stopLabel = new Label("Stop");
        TextField stopField = new TextField(2);
        Label stepLabel = new Label("Step");
        TextField stepField = new TextField(2);

    public myCheckerboard()
    {
        this.setLayout(new BorderLayout());
            boardPanel.setLayout(new GridLayout(4,4,2,3));
            inputPanel.setLayout(new FlowLayout());
            buttonPanel.setLayout(new FlowLayout(FlowLayout.LEFT));

            for (int i=0; i<16; i++)
            {
                boardDisplay[i] = new TextArea(null,3,5,3);
                if(i<16)
                    boardDisplay[i].setText("" + i);
                    boardDisplay[i].setEditable(false);
                    boardDisplay[i].setBackground(Color.white);
                    boardPanel.add(boardDisplay[i]);
            }

            //add components to the button
            buttonPanel.add(goButton);

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

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

            goButton.addActionListener(this);

            addWindowListener(
                new WindowAdapter()
                {
                    public void windowClosing(WindowEvent e)
                    {
                        System.exit(0);
                    }
                }
                );
            }//end of constructor

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

            public void actionPerformed(ActionEvent e)
            {
                if(i>15)
                {
                    JOptionPane.showMessageDialog(null, "You must enter a value less than 15.","Error",JOptionPane.ERROR_MESSAGE);
                }
                else
                {
                    start = Integer.parseInt(startField.getText());
                    stop = Integer.parseInt(stopField.getText());
                       step = Integer.parseInt(stepField.getText());
                }
                for (int i = 0; i <15; i++)
                {
                    panelDisplay[i].setBackground(Color.magenta);
                }
                for(int i = start; i < stop; i += step)
                {
                    panelDisplay[i].setBackground(Color.yellow);
                }
            }
        }