Problem With Highlighter

Question

Some help here would be appreciated. Attached it a simple textArea with a highlighter. My problem is that once you add some highlighted text, the highlighter still gets applied to all plain text that follows. I wouldn't have expected this behavior.
If you switch to the commented out textArea.append line in addHighlightedTextButtonActionPerformed it works fine except of course I'm not highlighting all of the text I would like.
Any thoughts as to why this is happening?
package test;
import java.awt.Color;
import java.awt.Font;
import javax.swing.JTextArea;
import javax.swing.text.DefaultHighlighter;
public class NewJFrame extends javax.swing.JFrame {
    public NewJFrame() {
        initComponents();
        textArea.setFont(new Font("Tahoma", 0, 11));
    @SuppressWarnings("unchecked")
    private void initComponents() {
        jScrollPane1 = new javax.swing.JScrollPane();
        textArea = new javax.swing.JTextArea();
        addHighlightedTextButton = new javax.swing.JButton();
        addTextButton = new javax.swing.JButton();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        textArea.setColumns(20);
        textArea.setRows(5);
        jScrollPane1.setViewportView(textArea);
        addHighlightedTextButton.setText("Add highlighted text");
        addHighlightedTextButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                addHighlightedTextButtonActionPerformed(evt);
        addTextButton.setText("Add text");
        addTextButton.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                addTextButtonActionPerformed(evt);
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 446, Short.MAX_VALUE)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(addTextButton)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(addHighlightedTextButton)))
                .addContainerGap())
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 312, Short.MAX_VALUE)
                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(addHighlightedTextButton)
                    .addComponent(addTextButton))
                .addContainerGap())
        pack();
    private void addHighlightedTextButtonActionPerformed(java.awt.event.ActionEvent evt) {
        int start = textArea.getText().length();
        String string = "highlighted text";
        textArea.append(string);
        try {
            textArea.getHighlighter().addHighlight(start, start + string.length(), new DefaultHighlighter.DefaultHighlightPainter(Color.RED));
//            textArea.getHighlighter().addHighlight(start, start + string.length() - 1, new DefaultHighlighter.DefaultHighlightPainter(Color.RED));
        } catch (Exception e) {
            e.printStackTrace();
    private void addTextButtonActionPerformed(java.awt.event.ActionEvent evt) {
        String string = "plain text";
        textArea.append(string);
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame().setVisible(true);
    // Variables declaration - do not modify
    private javax.swing.JButton addHighlightedTextButton;
    private javax.swing.JButton addTextButton;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea textArea;
    // End of variables declaration
}

Answer 1

Here is an example. MyHighlightPainter's paintLayer() method is a ripoff of DefaultHighlightPainter's version, but it knows to draw 1 offset "too far:"
import java.awt.*;
import javax.swing.*;
import javax.swing.text.*;
public class HighlighterExample extends JFrame {
     public HighlighterExample() {
          JPanel cp = new JPanel();
          JTextArea textArea = new JTextArea(20, 50);
          cp.add(new JScrollPane(textArea));
          String text = "This text has a higlight at the end of it.\n" +
               "Normally, if you append to text in a text component just after\n" +
               "a higlight, it gets absorbed into the highlight, thus extending\n" +
               "it.  But this higlight won't do that.\n" +
               "Try appending to me and see";
          textArea.setText(text);
          int start = text.length()-5;
          int end = text.length();
          end--; // MyHighlighter knows to draw to (end+1).
          Highlighter h = textArea.getHighlighter();
          MyHighlightPainter p = new MyHighlightPainter();
          try {
               h.addHighlight(start, end, p);
          } catch (BadLocationException ble) {
               ble.printStackTrace();
          setContentPane(cp);
          setTitle("Highlighter Example");
          setDefaultCloseOperation(EXIT_ON_CLOSE);
          pack();
     public static void main(String[] args) {
          SwingUtilities.invokeLater(new Runnable() {
               public void run() {
                    new HighlighterExample().setVisible(true);
     private class MyHighlightPainter extends DefaultHighlighter.DefaultHighlightPainter {
          public MyHighlightPainter() {
               super(Color.ORANGE);
          public Shape paintLayer(Graphics g, int p0, int p1, Shape viewBounds,
                    JTextComponent c, View view) {
               g.setColor(getColor());
               p1++; // Workaround for Java Highlight issues.
               if (p0 == view.getStartOffset() && p1 == view.getEndOffset()) {
                    // Contained in view, can just use bounds.
                    Rectangle alloc;
                    if (viewBounds instanceof Rectangle) {
                         alloc = (Rectangle) viewBounds;
                    } else {
                         alloc = viewBounds.getBounds();
                    g.fillRect(alloc.x, alloc.y, alloc.width - 1, alloc.height - 1);
                    return alloc;
               // Should only render part of View.
               try {
                    // --- determine locations ---
                    Shape shape = view.modelToView(p0, Position.Bias.Forward, p1,
                              Position.Bias.Backward, viewBounds);
                    Rectangle r = (shape instanceof Rectangle) ? (Rectangle) shape
                              : shape.getBounds();
                    g.fillRect(r.x, r.y, r.width - 1, r.height - 1);
                    return r;
               } catch (BadLocationException e) { // Never happens
                    e.printStackTrace();
                    return null;
}