Enforce max characters on Swing JTextArea with a few curve balls

Question

I\'m trying to add functionality to a Swing JLabel and JTextArea such that:

• The user is only allowed to enter 500 characters into the textarea (max)
• T

Answer 1

evt.consume(); will help alot in this case..you dont need to use DocumentFilter. here is a much easier way of limiting user at certain length

private void jTextArea1KeyTyped(java.awt.event.KeyEvent evt) {                                    
    String s=jTextArea1.getText();
   int l=s.length();
   jTextField1.setText(String.valueOf(l));
   int i=10-l;
   jTextField2.setText(String.valueOf(i));
   try{
   if(l>=10){evt.consume();
   }
   }
   catch(Exception w){}

} 

Answer 2

To add on to what Ray S. Kan said:

There is an easier way to limit the characters for a JTextArea without having to use a DocumentFilter as shown by Ray S. Kan, but the issue with his answer is that it does not prevent someone from pasting in a long text. The following will prevent a user from pasting in stuff to bypass the limit:

@Override
public void keyTyped(KeyEvent e) {
    int max = 25;
    if(text.getText().length() > max+1) {
        e.consume();
        String shortened = text.getText().substring(0, max);
        text.setText(shortened);
    }else if(text.getText().length() > max) {
        e.consume();
    }
}

This will stop a key from being pressed if the length is not pass max, but if it passes max, it will simply replace the string in the text area with a shorter string. The text variable is the JTextArea swing object.

Answer 3

You can limit the max size by using a DocumentFilter, check this documentation section, it has a working example of what you need.

Take this as an example, I used the component from the example file above:

import java.awt.BorderLayout;

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

import components.DocumentSizeFilter;

public class Test {

    public static void main(String[] args) {
        new TestFrame().setVisible(true);
    }

    private static class TestFrame extends JFrame{
        private JTextField textField;
        private DefaultStyledDocument doc;
        private JLabel remaningLabel = new JLabel();

        public TestFrame() {
            setLayout(new BorderLayout());

            textField = new JTextField();
            doc = new DefaultStyledDocument();
            doc.setDocumentFilter(new DocumentSizeFilter(500));
            doc.addDocumentListener(new DocumentListener(){
                @Override
                public void changedUpdate(DocumentEvent e) { updateCount();}
                @Override
                public void insertUpdate(DocumentEvent e) { updateCount();}
                @Override
                public void removeUpdate(DocumentEvent e) { updateCount();}
            });
            textField.setDocument(doc);

            updateCount();

            add(textField, BorderLayout.CENTER);
            add(remaningLabel, BorderLayout.SOUTH);

            setLocationRelativeTo(null);
            pack();
        }

        private void updateCount()
        {
            remaningLabel.setText((500 -doc.getLength()) + " characters remaining");
        }
    }
}