How do I format JTextField's text to uppercase?
Category: javax.swing, viewed: 10190 time(s).
The process to change the JTextField's text to some other format like upper case for instance can be easily done by adding a DocumentFilter to the text field component. The DocumentFilter allow us to do a filter action for changes in the document such as insert, replace and remove.
In this example we describe how to do it.
package org.kodejava.example.swing;
import javax.swing.text.DocumentFilter;
import javax.swing.text.BadLocationException;
import javax.swing.text.AttributeSet;
import javax.swing.text.AbstractDocument;
import javax.swing.*;
import java.awt.*;
public class DocumentFilterExample extends JFrame {
public DocumentFilterExample() throws HeadlessException {
initComponents();
}
protected void initComponents() {
setSize(200, 200);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
getContentPane().setLayout(new FlowLayout(FlowLayout.LEFT));
DocumentFilter filter = new UppercaseDocumentFilter();
JTextField firstName = new JTextField();
firstName.setPreferredSize(new Dimension(100, 20));
((AbstractDocument) firstName.getDocument()).setDocumentFilter(filter);
JTextField lastName = new JTextField();
lastName.setPreferredSize(new Dimension(100, 20));
((AbstractDocument) lastName.getDocument()).setDocumentFilter(filter);
getContentPane().add(firstName);
getContentPane().add(lastName);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new DocumentFilterExample().setVisible(true);
}
});
}
class UppercaseDocumentFilter extends DocumentFilter {
//
// Override insertString method of DocumentFilter to make the text format
// to uppercase.
//
public void insertString(DocumentFilter.FilterBypass fb, int offset,
String text, AttributeSet attr)
throws BadLocationException {
fb.insertString(offset, text.toUpperCase(), attr);
}
//
// Override replace method of DocumentFilter to make the text format
// to uppercase.
//
public void replace(DocumentFilter.FilterBypass fb, int offset, int length,
String text, AttributeSet attrs)
throws BadLocationException {
fb.replace(offset, length, text.toUpperCase(), attrs);
}
}
}
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