import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.HeadlessException;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
public class Main extends JFrame {
public Main() throws HeadlessException {
setSize(200, 200);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
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);
add(firstName);
add(lastName);
}
public static void main(String[] args) {
new Main().setVisible(true);
}
}
class UppercaseDocumentFilter extends DocumentFilter {
public void insertString(DocumentFilter.FilterBypass fb, int offset, String text,
AttributeSet attr) throws BadLocationException {
fb.insertString(offset, text.toUpperCase(), attr);
}
public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text,
AttributeSet attrs) throws BadLocationException {
fb.replace(offset, length, text.toUpperCase(), attrs);
}
}