Deleting a non-integer character in a TextField

Question

I'm new to java and I'm trying to make a simple program that will delete the user's input on a textfield if it is not an integer.

private void jTextField4KeyPressed(java.awt.event.KeyEvent evt) {   
    int j;
    try {
        j = Integer.parseInt(jTextField4.getText());
    }
    catch (NumberFormatException f) {
      jOptionPane1.showMessageDialog(null, "AwtsuPaytsu");
      jTextField4.setText("");
    }
}

It successfully deletes non-integer inputs automatically. However, it also deletes integer inputs. What should I do? I really need help. I want to learn.

You want any help about the user can only type integer values into textfield? — ravibagul91, Feb 01 '14 at 14:57
Use a `JSpinner` as seen [here](http://stackoverflow.com/a/10021773/418556). — Andrew Thompson, Feb 01 '14 at 23:02

ravibagul91 · Answer 1 · 2014-02-02T10:17:53.333

Look at this example this will only accept numbers from user. Here I have used Document Filter to accept only numbers and not other.

import java.awt.*;
import java.awt.event.KeyEvent;
import javax.swing.*;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException; 
import javax.swing.text.DocumentFilter;
import javax.swing.text.DocumentFilter.FilterBypass;

public class InputInteger
{
private JTextField tField;
private JLabel label=new JLabel();
private MyDocumentFilter documentFilter;

private void displayGUI()
{
    JFrame frame = new JFrame("Input Integer Example");
    frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

    JPanel contentPane = new JPanel();
    contentPane.setBorder(
        BorderFactory.createEmptyBorder(5, 5, 5, 5));
    tField = new JTextField(10);
    ((AbstractDocument)tField.getDocument()).setDocumentFilter(
            new MyDocumentFilter());

    contentPane.add(tField); 
    contentPane.add(label);


    frame.setContentPane(contentPane);
    frame.pack();
    frame.setLocationByPlatform(true);
    frame.setVisible(true);
}
public static void main(String[] args)
{
    Runnable runnable = new Runnable()
    {
        @Override
        public void run()
        {
            new InputInteger().displayGUI();
        }
    };
    EventQueue.invokeLater(runnable);
}
}

class MyDocumentFilter extends DocumentFilter{
    private static final long serialVersionUID = 1L;
    @Override
public void insertString(FilterBypass fb, int off
                    , String str, AttributeSet attr) 
                            throws BadLocationException 
{
    // remove non-digits
    fb.insertString(off, str.replaceAll("\\D++", ""), attr);
} 
@Override
public void replace(FilterBypass fb, int off
        , int len, String str, AttributeSet attr) 
                        throws BadLocationException 
{
    // remove non-digits
    fb.replace(off, len, str.replaceAll("\\D++", ""), attr);
}
}

Useful link

Implementing a Document Filter

I'm just a beginner. Please put something that I can easily understand. — user3260589, Feb 01 '14 at 15:10
@user3260589 using keyListener on TextField is not a good practice, you have to go with the proper way, and proper way is to use the Document Listener. Just go thr' the link above or search for document listener on Google you will get it. — ravibagul91, Feb 01 '14 at 16:29
+1 for the documentFilter, -1 for still having a (unneeded) keyListener, zeroes out ;) — kleopatra, Feb 02 '14 at 10:01
@user3260589 if you don't understand this simple example you might consider not coding at all .. anyway, there's no way around reading a decent textbook/tutorial to learn the basics - there's reference to a good online tutorial in the swing tag wiki — kleopatra, Feb 02 '14 at 10:03
@kleopatra Here `keyListener` is just for setting the `label` value as we type in `jTextField`, one can remove it. Actually there is no need to use `keyListener` at all. — ravibagul91, Feb 02 '14 at 10:09
_Actually there is no need to use keyListener at all_ agreed. Hint: you can edit your answer, as you know :-) — kleopatra, Feb 02 '14 at 10:14

udit bansal · Answer 2 · 2014-02-01T14:55:14.127

So you want to remove all the non-digits from the string and set that again in text field. You can try the following.

private void jTextField4KeyPressed(java.awt.event.KeyEvent evt) {   
    String str = jTextField4.getText();
    StringBuilder str1 = new StringBuilder();

    for(int i = 0; i <= str.length() - 1; ++i) {

        if(!Character.isLetter(str.charAt(i))) {
            str1.append(str.charAt(i));
        }
            else {
                jOptionPane1.showMessageDialog(null, "AwtsuPaytsu");
            }

    }
    jTextField4.setText(str1);

}

score 0 · Answer 3 · edited May 23 '17 at 10:25

Even if i think Jugadus approach here is the right one. (not enough rep for commenting sorry)

It seems to be quite a bit too much for the questioner.

In my opinion fixing it after it has been written is just a bad approach.

I think you should take a look at:

https://stackoverflow.com/a/11093360/661142

By using keyListeners you're missing quite a few things (like pasting etc)

or use a JFormattedTextField for that purpose like in:

https://stackoverflow.com/a/16228698/661142

Mohammed Alokshiya · Answer 4 · 2014-02-01T15:30:37.650

-1

From jTextField events, choose keyReleased event not keyPressed! And put this code inside the new generated handler:

private void keyReleased(java.awt.event.KeyEvent evt) {                             
    try {
        Integer.parseInt(jTextField2.getText());
    } catch (NumberFormatException f) {
        if (!jTextField2.getText().isEmpty())
            JOptionPane.showMessageDialog(null, "AwtsuPaytsu");
        jTextField2.setText(jTextField2.getText().replaceAll("[^0-9]", ""));
        //jTextField2.setText("");
    }
}

keyReleased event

edited Feb 01 '14 at 15:30

answered Feb 01 '14 at 15:17

Mohammed Alokshiya

643
6
12

New problem is when I pressed backspace, the MessageDialog comes out. That is not supposed to happen. – user3260589 Feb 01 '14 at 15:19
be sure to remove the previous keyPressed event! – Mohammed Alokshiya Feb 01 '14 at 15:21
-1 for keyListener - that's **not** the correct way to restrict input: one reason is that it is completely safe as it doesn't catch pasted text – kleopatra Feb 02 '14 at 09:59

score -2 · Answer 5 · answered Feb 01 '14 at 14:33

-2

Try:

jTextField4.setText(jTextField4.getText().replaceAll("[^0-9]", ""));

answered Feb 01 '14 at 14:33

Mohammed Alokshiya

643
6
12

Almost there. However, the MessageDialog still appears when I entered an integer. – user3260589 Feb 01 '14 at 14:44
use KeyReleased event instead of KeyPressed – Mohammed Alokshiya Feb 01 '14 at 15:08
Works! However, when I accidentally pressed backspace, the MessageDialog comes out. – user3260589 Feb 01 '14 at 15:17
Are you sure you removed all unnecessary events? like keyPressed? It works fine for me, and I can press backspace without any problems ^_^ – Mohammed Alokshiya Feb 01 '14 at 15:19
Yep, I've removed other useless events. :) It works just fine now but when you press backspace when the TextField is empty, the MessageDialog comes out. – user3260589 Feb 01 '14 at 15:24
add an if statement to check if the textField is empty, if so, don't show MessaeDialog. only show it when textField is not empty. like this: if (!jTextField2.getText().isEmpty()) JOptionPane.showMessageDialog(null, "AwtsuPaytsu"); – Mohammed Alokshiya Feb 01 '14 at 15:29
Yeah! Thanks! Kudos! Arigatou! Thank you so much :D – user3260589 Feb 01 '14 at 15:43

Deleting a non-integer character in a TextField

5 Answers5