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How can we limit the number of characters inside a JTextField in Java?
A JTextFeld is one of the most important components that allow the user to an input text value in a single line format. We can restrict the number of characters that the user can enter into a JTextField can be achieved by using a PlainDocument class.
In the below example, we can implement the logic by using a PlainDocument class, hence we can allow a user to enter a maximum of 10 characters, it doesn't allow if we enter more than 10 characters.
Example
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
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 JTextFieldLimitTest extends JFrame {
JTextField textfield;
JLabel label;
public static void main(String[]args){
new JTextFieldLimitTest().GUI();
}
public void GUI() {
setLayout(new FlowLayout());
label = new JLabel("max 10 chars");
textfield = new JTextField(15);
add(label);
add(textfield);
textfield.setDocument(new JTextFieldLimit(10));
setSize(350,300);
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
}
}Output
Updated on: 07-Feb-2020
3K+ Views
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