Max number of characters in a JTextField

I don't want to alowe more than 4 characters in a JTextField.
Is where any method in Java corresponding to maxlength for textbox in Visual Basic??
Or do I have to use KeyListener to check the situation for every key pressed?
I'll be thankful for any help.

write your own document & override the insertString() like the one below:
import javax.swing.text.*;
public class MyDocument extends PlainDocument {
     public void insertString(int offs, String s, AttributeSet a)
                                                      throws BadLocationException {
          if(getLength() > 4)
          //if(offs > 3)
          //if(getText(0, getLength()).length() > 4)
               return;
          else
               super.insertString(offs, s, a);
}

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Hi,
I know this question has been posted several times on this forum, but my question is actually a different one. So please read.
I have the following code that puts two JTextFields in a JFrame. I want to limit the number of characters in the first JTextField to three characters. What's different about my question from other solutions provided, is that I don't want to be able to type more than three characters in the JTextField, and then not be able to get out of JTextField unless I have three or less characters. What I do want, is to have maximum of three characters, not be able to type the fourth, and have access to the other JTextField at all times.
I have tried the following solution of setting an InputVerifier to my JTextField, but it hasn't worked, since I can still type the fourth character.
Looking forward to your help!
Thanks.
import java.awt.Dimension;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import javax.swing.InputVerifier;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class TextFieldVerifier {
     public TextFieldVerifier()
          JFrame frame = new JFrame("My TextVerifier");
          JPanel panel = new JPanel();
          JLabel firstTextFieldLabel = new JLabel("First: ");
          JLabel secondTextFieldLabel = new JLabel("Second: ");
          final JTextField myTextField = new JTextField();
          myTextField.setPreferredSize(new Dimension(100,20));
          myTextField.setInputVerifier(new InputVerifier()
               public boolean verify(JComponent input) {
                    if(myTextField.getText().length()<=3)
                         return true;
                    else
                        return false;
          myTextField.addKeyListener(new KeyAdapter()
               public void keyTyped(KeyEvent e)
                    if(!myTextField.getInputVerifier().verify(myTextField))
                         myTextField.setText(myTextField.getText().substring(0, myTextField.getText().length()-1));
          JTextField secondTextField = new JTextField();
          secondTextField.setPreferredSize(new Dimension(100,20));
          panel.add(firstTextFieldLabel);
          panel.add(myTextField);
          panel.add(secondTextFieldLabel);
          panel.add(secondTextField);
          frame.getContentPane().add(panel);
          frame.setSize(new Dimension(200,100));
          frame.setVisible(true);
     public static void main (String [] args)
          TextFieldVerifier v = new TextFieldVerifier();
}

Thanks, JayDS! Your suggestion worked. And I've come up with the following code with help of your suggestion. However, I'm not happy with the fact that I see empty spaces in my JFormattedTextField when I don't have anything entered in it, or when my textfield has focus and I click it again. Also, I'd like the text alignment to always stay on the right, even if I have less than 3 digits.
Could you please help me out with that?
Thanks!
import java.awt.Dimension;
import java.text.ParseException;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.text.MaskFormatter;
public class TextFieldVerifier {
     public TextFieldVerifier()
          JFrame frame = new JFrame("My TextVerifier");
          JPanel panel = new JPanel();
          JLabel firstTextFieldLabel = new JLabel("First: ");
          JLabel secondTextFieldLabel = new JLabel("Second: ");
          try{
               VariableLengthMaskFormatter formatter = new VariableLengthMaskFormatter("###");
               final JFormattedTextField myTextField = new JFormattedTextField(formatter);
               myTextField.setHorizontalAlignment(JTextField.RIGHT);
               myTextField.setPreferredSize(new Dimension(100,20));
               panel.add(firstTextFieldLabel);
               panel.add(myTextField);
          } catch (ParseException ex) {
               ex.printStackTrace();
          JTextField secondTextField = new JTextField();
          secondTextField.setPreferredSize(new Dimension(100,20));
          panel.add(secondTextFieldLabel);
          panel.add(secondTextField);
          frame.getContentPane().add(panel);
          frame.setSize(new Dimension(200,100));
          frame.setVisible(true);
     protected MaskFormatter createFormatter(String s) {
         MaskFormatter formatter = null;
         try {
              formatter = new MaskFormatter(s);
         } catch (java.text.ParseException exc) {
             System.err.println("formatter is bad: " + exc.getMessage());
             System.exit(-1);
         return formatter;
     public static void main (String [] args)
          TextFieldVerifier v = new TextFieldVerifier();
}Edited by: programmer_girl on Mar 10, 2008 11:10 PM

Limit number of characters in a JTextField

Now I know that this question has been asked very often but the answers that have been given do not always work. According to other posts you can either use a KeyListener or a DocumentListener. The problem with the code that I have seen using a KeyListener is that you can't use the backspace key when the limit is reached. I am using a JTextField and all the answers dealing with Documents use a JTextArea and I can't figure out how to get it to work with JTextField. I don't understand why the Swing package just didn't come out with a method or cunstructor for these components to limit the number of characters. It would simplify things a lot. I need a JTextField to allow only 25 characters and allow backspaces. Thanks

Here is the code that I am using. It seems to be working somewhat. The only problem now is that when you type the 26th key that new key overwrites what is in the 25th position. Is this the correct way of doing it and if so how do I get it to quit adding in the key that was just pressed?
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Hi I have 6 textfields and I don't want the user to enter more than 160 characters in a tet box. As soon as he reaches that limit, it shouldn't accept any more characters, how do I do this?
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The event generated from the textboxes has a method e.getSource() check that.
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Hi,
I am new to java and I would like to create a JTextField which only allows the users to enter no more than 32 characters. How do I do that? I am looking for a "set..." function but cannot find it.
Thanks for any hint.
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import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
public class Limit {
public static void main(String args[]) {
new LimitFrame();
class LimitFrame extends JFrame {
JTextField jtf = new JTextField(10);
LimitFrame() {
super();
jtf.setDocument(new LimitDocument(5));
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Container cp = getContentPane();
cp.add(BorderLayout.NORTH,jtf);
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pack();
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int limit;
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Hello,
Can anyone tell me how to restrict the number of characters that a JTextField can have?
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read this: [http://java.sun.com/docs/books/tutorial/uiswing/components/formattedtextfield.html]
and this: [http://java.sun.com/docs/books/tutorial/uiswing/misc/focus.html#inputVerification]

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Hi All,
I have an input field.
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need your helpful answers
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Srinivas

Hi Srinu
You could achieve this by configuring error messages under the formula:-
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Regards
Navneet
Message was edited by:
Navneet Giria

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How to limit the number of characters entered in a JTextfield???

Hello there,
I have created a Text box using swing component JTextField and I want to limit the number of characters entered to 8 characters..how do i proceed with that?
Thanks in advance!
Joe

Ty out this
import com.sun.java.swing.text.*;
//import javax.swing.text.*;
public class JTextFieldLimit extends PlainDocument {
private int limit;
// optional uppercase conversion
private boolean toUppercase = false;
JTextFieldLimit(int limit) {
super();
this.limit = limit;
JTextFieldLimit(int limit, boolean upper) {
super();
this.limit = limit;
toUppercase = upper;
public void insertString
(int offset, String str, AttributeSet attr)
throws BadLocationException {
if (str == null) return;
if ((getLength() + str.length()) <= limit) {
if (toUppercase) str = str.toUpperCase();
super.insertString(offset, str, attr);
import java.awt.*;
import com.sun.java.swing.*;
//import javax.swing.*;
public class tswing extends JApplet{
JTextField textfield1;
JLabel label1;
public void init() {
getContentPane().setLayout(new FlowLayout());
label1 = new JLabel("max 10 chars");
textfield1 = new JTextField(15);
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textfield1.setDocument
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How can the number of characters typed on a component (for example a multi line text area) limited? (such a way if the limit reaches then the keyboard should not be responded)
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Hi,
In the properties sheet, under the data section, the length validator is available. The length validator does not stop the user from entering after the max length has been reached. Once submitted the validator will be invoked and an error message displayed. An RFE has been filed on your behalf for the same.
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Max number of characters in a JTextField

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