Programa que procura palavras em texto e as coloca em negrito

package swingtests;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextPane;
import javax.swing.text.DefaultStyledDocument;
import javax.swing.text.Style;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyleContext;

public class CompilerEditor {

    private DefaultStyledDocument doc = null;

    private StyleContext sc = null;

    private Style defautStyle = null;

    private Style mainStyle = null;

    private JTextPane texto;

    public CompilerEditor(JTextPane texto) {

        sc = new StyleContext();
        doc = new DefaultStyledDocument(sc);
        texto.setStyledDocument(doc);

        defautStyle = sc.getStyle(StyleContext.DEFAULT_STYLE);
        mainStyle = sc.addStyle("MainStyle", defautStyle);

        StyleConstants.setBold(mainStyle, true);
        StyleConstants.setForeground(mainStyle, Color.BLUE);

        this.texto = texto;

    }

    public void executa(ArrayList<String> palavras) {

        processaTexto(analisaTexto(palavras));

    }

    private void processaTexto(ArrayList<Point> points) {

        System.out.println(points);

        doc.setLogicalStyle(0, mainStyle);
        for (Point p : points) {
            doc.setCharacterAttributes(p.x, p.y, mainStyle, false);
        }

    }

    private ArrayList<Point> analisaTexto(ArrayList<String> palavras) {

        ArrayList<Point> onde = new ArrayList<Point>();
        int pinicial = -1;
        int pfinal = -1;

        for (String s : palavras) {

            String substr = texto.getText();

            do {
                pinicial = substr.indexOf(s);

                System.out.println(substr);
                if (pinicial != -1) {

                    pfinal = pinicial + s.length();
                    substr = substr.substring(pfinal);
                    onde.add(new Point(pinicial, s.length()));
                    pfinal = -1;
                }

            } while (pinicial != -1);
        }

        return onde;
    }
}

class RunCompiler {
    public static void main(String[] args) {

        final JTextPane text = new JTextPane();

        final ArrayList<String> words = new ArrayList<String>();
        final CompilerEditor compiler = new CompilerEditor(text);

        words.add("case");
        words.add("if");
        words.add("while");

        try {
            text
                    .setPage("http://www.cs.unc.edu/~huan/comp14/TelephoneDigitProgram.java");
        } catch (Exception e) {
            e.printStackTrace();

        }

        JFrame f = new JFrame();

        JScrollPane scroll = new JScrollPane(text);

        f.setLayout(new BorderLayout());
        f.setSize(400, 400);
        JButton button = new JButton("Processa");
        f.add(scroll, "Center");
        f.add(button, "South");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);

        button.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                compiler.executa(words);
                System.out.println("dentro do evento do button");
            }

        });

    }
}