Limit JTextField input to a maximum length : TextField « Swing JFC « Java

Limit JTextField input to a maximum length

import java.awt.FlowLayout;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;

class JTextFieldLimit extends PlainDocument {
  private int limit;
  JTextFieldLimit(int limit) {
    this.limit = limit;

  JTextFieldLimit(int limit, boolean upper) {
    this.limit = limit;

  public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException {
    if (str == null)

    if ((getLength() + str.length()) <= limit) {
      super.insertString(offset, str, attr);

public class Main extends JFrame {
  JTextField textfield1;

  JLabel label1;

  public void init() {
    setLayout(new FlowLayout());
    label1 = new JLabel("max 10 chars");
    textfield1 = new JTextField(15);
    textfield1.setDocument(new JTextFieldLimit(10));


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