Selecting two JText Area at a time

Question

Hi All,
I am creating an GUI application for diff'ing two text files. For showing the two text files I am using the JTextArea and now the problem is when I show difference between two fields I have to select text in the two JTextArea Simultaneously so that we can see the differences between two lines. but I don't know how to select two Jtext area at a time.
Please help me doing this.
If not possible somebody please suggest me some alternative for this.
Regards,
Anoop

Answer 1

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
public class HighlightText extends JFrame {
    private JTextArea textarea1;
    private JTextArea textarea2;
    private JButton pressJButton;
    public HighlightText() {
        super( "Highlight Text" );
        Box box = Box.createHorizontalBox();
        final String s = "Here is the first line.\n" +
                "Here is the second line.\n" +
                "Here is the third line.\n" +
                "Here is the fourth line.\n";
        textarea1 = new JTextArea(s);
        box.add( new JScrollPane( textarea1 ) );
        textarea2 = new JTextArea(s);
        box.add( new JScrollPane( textarea2 ) );
        pressJButton = new JButton( "Press" );
        box.add(pressJButton );
        highlight(textarea1, 12,17);
        highlight(textarea2, 12,17);
        pressJButton.addActionListener(
                new ActionListener() {
            public void actionPerformed( ActionEvent event ) {
                highlight(textarea1, 36,42);
                highlight(textarea2, 36,42);
        getContentPane().add(box);
        setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        setSize( 600, 300 );
        setLocationRelativeTo(null);
    public static void main( String args[] ) {
        new HighlightText().setVisible(true);
    // Creates highlights
    private void highlight(JTextComponent textComp, int selectionStart, int selectionEnd) {
        // First remove all old highlights
        removeHighlights(textComp);
        try {
            Highlighter hilite = textComp.getHighlighter();
            // Add highlight using private painter
            currentHilite = hilite.addHighlight(selectionStart, selectionEnd, textPainter);
        } catch (BadLocationException e) {
    private Object currentHilite;
    // Removes only our private highlights
    private void removeHighlights(JTextComponent textComp) {
        Highlighter hilite = textComp.getHighlighter();
        Highlighter.Highlight[] hilites = hilite.getHighlights();
        for (int index=0; index<hilites.length; index++) {
            if (hilites[index].getPainter() instanceof TextPainter) {
                hilite.removeHighlight(hilites[index]);
    // An instance of the private subclass of the default highlight painter
    private Highlighter.HighlightPainter textPainter = new TextPainter(Color.yellow);
    // A private subclass of the default highlight painter
    private class TextPainter extends DefaultHighlighter.DefaultHighlightPainter {
        public TextPainter(Color color) {
            super(color);
}