JOptionPane and reading integers - Beginner Java

Question

I currently have code that reads the month, date, and year a user enters in one line (separated by spaces). Here is the code.

Scanner input = new Scanner(Sys         


        

Answer 1

Here's some code, everything is described in the comments:

// import statements
import javax.swing.JOptionPane;
// main class
public class Main {
    // main method
    public static void main(String[] args) {
        // get info
        try {
            Info info = new Info();
        } catch(Exception e) {
            System.err.println("Error! " + e.getMessage());
        }
        // do whatever with the info
    }
    // info class
    static class Info {
        // instance variables
        public int day, month, year;
        // constructor
        public Info() throws Exception {
            // get inputs
            String[] inputs = JOptionPane.showInputDialog(null, 
                "Enter day, month, year").split(" ");
            // not the right size
            if(inputs.length != 3) {   
                throw new Exception("Not enough infomation was given!");
            }
            // get values
            day = Integer.parseInt(inputs[0]);
            month = Integer.parseInt(inputs[1]);
            year = Integer.parseInt(inputs[2]);
        }
    }
}

It has an elegant way of notifying you if something went wrong, and everything you need is packaged up in a convenient object.

Answer 2

You can make use of following to take user input

String word = JOptionPane.showInputDialog("Enter 3 int values");
String[] vals = word.split("\\s+"); // split the sting by whitespaces accepts regex. 
// vals[0] cast to int
// convert string representation of number into actual int value
int day = Integer.parseInt(vals[0]); // throws NumberFormatException
// vals[1] cast to int
// vals[2] cast to int

split Java API

parseInt Java API

Java Regex Tutorial

Answer 3

There are a number of ways to approach the problem depending on ultimately what it is you want to achieve.

JOptionPane allows you to supply Object as the message. If this message is a String it will rendered as is, however, if it is a Component of some kind, it will be simply added to the dialog. This makes JOptionPane a very powerful little API.

public class TestOptionPane07 {

    public static void main(String[] args) {
        new TestOptionPane07();
    }

    public TestOptionPane07() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JTextField fldDay = new JTextField(3);
                JTextField fldMonth = new JTextField(3);
                JTextField fldYear = new JTextField(4);
                JPanel message = new JPanel();
                message.add(fldDay);
                message.add(new JLabel("/"));
                message.add(fldMonth);
                message.add(new JLabel("/"));
                message.add(fldYear);

                int result = JOptionPane.showConfirmDialog(null, message, "Enter Date", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE);
                if (result == JOptionPane.OK_OPTION) {
                    String sDay = fldDay.getText();
                    String sMonth = fldMonth.getText();
                    String sYear = fldYear.getText();
                    JOptionPane.showMessageDialog(null, "You enetered " + sDay + "/" + sMonth + "/" + sYear);

                    try {
                        int day = Integer.parseInt(sDay);
                        int month = Integer.parseInt(sMonth);
                        int year = Integer.parseInt(sYear);
                        JOptionPane.showMessageDialog(null, "You enetered " + day + "/" + month + "/" + year);
                    } catch (Exception e) {
                        JOptionPane.showMessageDialog(null, "The values you entered are invalid");
                    }
                }
            }
        });
    }
}

Updated

If I was going to use something like this, I would also use a DocumentFilter to ensure that the user could only enter valid values (examples here)

But you could also use JSpinners

Or JComboBox

Depending on what it is you want to achieve...