How can I know if the user is inserting a valid Date or not in Java's Swing?

Question

I am creating a project in which I am supposed to take date of birth of any person. So for that I have taken 3 combo boxes: date, month and year. But how I will know that the Date which is going to be inserted is valid because the number of day is different-different months and years is different.

And is there any ready made GUI component for taking dates from users?

I am designing using Swing package.

My sample code is

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

public class Pro1 extends JFrame
{

    JComboBox  dd, mm, yy;

    JLabel doblbl;

    Container con;

    public Pro1()
    {
        con = getContentPane(); 

        doblbl = new JLabel("Date of Birth :-");
        doblbl.setHorizontalAlignment(SwingConstants.CENTER);   

        doblbl.setFont(new Font("Arial",Font.BOLD,17));
        doblbl.setForeground(Color.blue);

        doblbl.setOpaque(true); 
        doblbl.setBackground(new Color(230,180,230));


        dd = new JComboBox();
        mm = new JComboBox();
        yy = new JComboBox();

        for(int i = 1; i<=31; i++)
            dd.addItem("" + i);

        for(int i = 1; i<=12; i++)
            mm.addItem("" + i);

        for(int i = 1960; i<=2014; i++)
            yy.addItem("" + i);


        con.setLayout(null); 

        setDefaultCloseOperation(EXIT_ON_CLOSE);    

        int i = 120;

        doblbl.setBounds(30,i+=40,270,30);

        int j = 120;

        dd.setBounds(350,j+=40,50,30);
        mm.setBounds(420,j,50,30);
        yy.setBounds(480,j,70,30);

        con.add(doblbl);

        con.add(dd);
        con.add(mm);
        con.add(yy);

        setSize(1500,800);
        setVisible(true);

        con.setBackground(new Color(125,80,140));           
    }

    public static void main(String s[])
    {
        Pro1 p1 = new Pro1();

    }
}

Answer 1

Consider offering the user a JSpinner with a SpinnerDateModel, then it is easier for the user to enter, or scroll through and select, a valid date.

import java.awt.*;
import java.util.*;
import javax.swing.*;

public class PromptForDate {

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(
                            UIManager.getSystemLookAndFeelClassName());
                } catch (Exception useDefault) {}
                SpinnerDateModel dateModel = new SpinnerDateModel(
                        new Date(), null, null, Calendar.DAY_OF_MONTH );
                JSpinner dateSpinner = new JSpinner(dateModel);
                dateSpinner.setEditor(
                        new JSpinner.DateEditor(dateSpinner, "dd/MM/yyyy"));

                JOptionPane.showMessageDialog(
                        null, dateSpinner, "D.O.B.?", 
                        JOptionPane.QUESTION_MESSAGE);

                System.out.println(dateModel.getValue());
            }
        };
        SwingUtilities.invokeLater(r);
    }
}

Answer 2

And is there any ready made GUI component for taking dates from users?

Yes, there are several options in standard API and third-party libraries, as exposed in this answer: JSpinner + SpinnerDateModel or JCalendar or JXDatePicker. These components will also solve this other problem:

But how i will know that the date which is going to be inserted is valid because the number of dates in different-different months and years is different.

---

Off-topic

About this:

con.setLayout(null);
...
dd.setBounds(350,j+=40,50,30);
mm.setBounds(420,j,50,30);
yy.setBounds(480,j,70,30);
...
con.add(dd);
con.add(mm);
con.add(yy);

While using Null layout is perfectly possible, Swing is designed to be used along with layout managers and thus null layout is discouraged. See this topic Why is it frowned upon to use a null layout in SWING?.

Answer 3

You can use SimpleDateFormat to parse or format the date as dd/MM/yyyy.

Sample code:

SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
String dateString = "30/02/2014"; // form date string in above format

String formattedDate = sdf.format(sdf.parse(dateString));
if (formattedDate.equals(dateString)) {
    System.out.println("valid date");
} else {
    System.out.println("Invalid date"); // It's an invalid date
}