Limit JTextField input to a maximum length : JTextField « Swing « Java Tutorial

1. Java Tutorial
2. Swing
3. JTextField

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) {
    super();
    this.limit = limit;
  }

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

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

    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);
    add(label1);
    add(textfield1);
    textfield1.setDocument(new JTextFieldLimit(10));
    
    setSize(300,300);
    setVisible(true);
  }
}

14.15.JTextField
	14.15.1.	Make a Text Field two columns wide
	14.15.2.	Sharing Data Models between two JTextField
	14.15.3.	Adding ActionListener to JTextField
	14.15.4.	Verifying Input During Focus Traversal
	14.15.5.	JTextField with a JScrollBar for Scrolling
	14.15.6.	Horizontal Alignment
	14.15.7.	Using JLabel Mnemonics: Interconnect a specific JLabel and JTextField
	14.15.8.	To make sure that the end of the contents is visible
	14.15.9.	Use the write() method to write the contents
	14.15.10.	Drag and drop Text Demo
	14.15.11.	Using Actions with Text Components: JTextField
	14.15.12.	HighLight painter and JTextField
	14.15.13.	Limit JTextField input to a maximum length
	14.15.14.	Apply special filter to a JTextField
	14.15.15.	Format JTextField's text to uppercase
	14.15.16.	Add key listener event handler to JTextField
	14.15.17.	Right justified JTextfield content
	14.15.18.	Set the focus on a particular JTextField
	14.15.19.	Customizing a JTextField Look and Feel
	14.15.20.	Cut, paste, and copy in a JTextField
	14.15.21.	Aligning the Text in a JTextField Component
	14.15.22.	Based on JTextField content, enable or disable a JButton
	14.15.23.	Subclass InputVerfier
	14.15.24.	extends JTextField to create integer JTextField