Looping

[chop vick]

New to java and having a problem getting my loop to work. program runs and stops the user from inputting anything less than zero but not stopping them from inputting anything over 1000.

Also having a problem with the NumberFormatException as i can't let user input letters either!

Once loop is working i then need to read user input in JOptionPane and pass it to a constructor in a different class.

First time on this so thanks for any help given!!

public class TestDraw3 extends JFrame {


    public static void main(String[] args) {

        int input = 0;
        String value = null;
        JOptionPane pane = new JOptionPane();
        boolean valid = true;

        value = JOptionPane.showInputDialog(null, "Enter the number of figures " +
                "to generate");

        try {
            input = Integer.parseInt(value);
            while (valid)


                if (input < 0) {
                    JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                            "non-numeric symbols!");
                    JOptionPane.showInputDialog(null, "Enter the number of figures" +
                            "to generate");
                    valid = false;

                    if (input > 1000) {
                        JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                                "non-numeric symbols!");
                        JOptionPane.showInputDialog(null, "Enter the number of figures" +
                                "to generate");
                        valid = false;

                    }
                    if (input > 0) {
                        input = Integer.parseInt(value);
                        valid = true;
                        System.exit(JOptionPane.CANCEL_OPTION);
                    }
                } else {
                    valid = true;
                }
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "The data you've entered contains" +
                    "non-numeric symbols!");
            JOptionPane.showInputDialog(null, "Enter the number of figures" +
                    "to generate");
        }

        DrawPanel3 panel = new DrawPanel3();
        JFrame application = new JFrame();

        JLabel label = new JLabel(panel.getShapesStatsString());
        JLabel label2 = new JLabel(panel.getShapesStatsString());

        label.setForeground(Color.BLACK);
        label2.setForeground(Color.BLACK);
        label.setBackground(Color.GRAY);
        label2.setBackground(Color.GRAY);
        Border border = BorderFactory.createLineBorder(Color.BLUE, 2);
        label.setBorder(border);
        label2.setBorder(border);

        application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        panel.add(label, BorderLayout.SOUTH);
        panel.add(label2, BorderLayout.NORTH);
        application.add(panel);
        application.setSize(500, 500);

        application.setVisible(true);


    }

}

[chop vick]

changed my code a bit and program now stops user from inputting anything over 1000. But how do i get it to stop user from inputting letters or words?!!\

int input = 0;
        String value = null;
        boolean valid = true;

        value = JOptionPane.showInputDialog(null, "Enter the number of figures " +
                "to generate");

        try {
            input = Integer.parseInt(value);
            while (valid)


                if (input < 0) {
                    JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                            "non-numeric symbols!");
                    JOptionPane.showInputDialog(null, "Enter the number of figures" +
                            "to generate");
                    valid = false;
                } else if (input > 1000) {
                    JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                            "non-numeric symbols!");
                    JOptionPane.showInputDialog(null, "Enter the number of figures" +
                            "to generate");
                    valid = false;
                } else if (input > 0) {
                    input = Integer.parseInt(value);
                    valid = true;
                    System.exit(JOptionPane.CANCEL_OPTION);
                } else if (value == null) {
                    JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                            "non-numeric symbols!");
                    JOptionPane.showInputDialog(null, "Enter the number of figures" +
                            "to generate");

                }
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                    "non-numeric symbols!");
            JOptionPane.showInputDialog(null, "Enter the number of figures" +
                    "to generate");

[Junilu Lacar]

Do you understand when the catch (NumberFormatException e) on line 36 will be executed?  Do you know how to use loops?

See Java Tutorial - Exceptions
See Java Tutorial - Loops

[chop vick]

ok so have came up with this now but loop finishes after user is prompted to enter new number after first input is invalid. what to do?

try {
            input = Integer.parseInt(value);

                if (input < 0) {
                    JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                            "non-numeric symbols!");
                    JOptionPane.showInputDialog(null, "Enter the number of figures" +
                            "to generate");
                    valid = false;
                } else if (input > 1000) {
                    JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                            "non-numeric symbols!");
                    JOptionPane.showInputDialog(null, "Enter the number of figures" +
                            "to generate");
                    valid = false;
                } else if (value == null) {
                    JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                            "non-numeric symbols!");
                    JOptionPane.showInputDialog(null, "Enter the number of figures " +
                            "to generate");
                    valid = false;
                } else if (input > 0) {
                    input = Integer.parseInt(value);
                    valid = true;
                    System.exit(JOptionPane.CANCEL_OPTION);
                }

        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "The data you've entered contains " +
                    "non-numeric symbols!");
            JOptionPane.showInputDialog(null, "Enter the number of figures" +
                    "to generate");

[Dave Tolls]

I don't see a loop in that latest code?

[Campbell Ritchie]

Welcome to the Ranch

I can see a problem, I am afraid. You have got a method inside a display component which isn't part of the display. Testing whether the input is a number or not is part of your “business logic” and ought to be in a “business class”. Which isn't the opposite of economy class. You shou‍ld have a method which tests whether the input is a number or not; the display class can take action, e.g. remove the entry from the text field.
There are better ways to test whether a String represents a number than catching Exceptions. You will find some suggestions in this thread from last Summer.