Java Swing - 如何un高亮JTextPane中的文本

import java.awt.Color;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JTextPane;
import javax.swing.text.DefaultHighlighter;
import javax.swing.text.Document;
import javax.swing.text.Highlighter;
import javax.swing.text.JTextComponent;

public class Main extends JFrame {

    public static void main(String args[]) {
       new Main().setVisible(true);
    }
    Highlighter.HighlightPainter myHighLightPainter=new MyHighightPainter(Color.LIGHT_GRAY);

    private JScrollPane scrollPane;
    private JTextField searchText;
    private JTextPane textPane;
    private JButton search;
    public Main() {
      search = new javax.swing.JButton();
      searchText = new javax.swing.JTextField();
      scrollPane = new javax.swing.JScrollPane();
      textPane = new javax.swing.JTextPane();
      searchText.setText("test");
      textPane.setText("this is a testtest ");

      setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

      search.setText("Search");
      search.addActionListener(new java.awt.event.ActionListener() {
          public void actionPerformed(java.awt.event.ActionEvent evt) {
              searchActionPerformed(evt);
          }
      });

      scrollPane.setViewportView(textPane);
      getContentPane().add(scrollPane,"Center");
      getContentPane().add(searchText,"North");
      getContentPane().add(search,"South");
      pack();
    }
    public void highLight(JTextComponent component,String patteren){
        try {
            Document doc=component.getDocument();
            String text=component.getText(0,doc.getLength());
            int pos=component.getCaretPosition();
            if (pos==doc.getLength()) {
                pos=0;
            }
            int index=text.toUpperCase().indexOf(patteren.toUpperCase(),pos);
            if (index>=0) {
                component.setSelectionStart(index);
                component.setSelectionEnd(index+patteren.length());
                component.getCaret().setSelectionVisible(true);
            }
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }
    private void searchActionPerformed(java.awt.event.ActionEvent evt) {
        highLight(textPane, searchText.getText());
    }    
}
class MyHighightPainter extends DefaultHighlighter.DefaultHighlightPainter{
  MyHighightPainter(Color color){
      super(color);
  }
}