JTextPane Java关键字变色

import java.util.StringTokenizer;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;
import javax.swing.text.rtf.RTFEditorKit;

public class MyTextPane extends JTextPane {

    protected StyleContext m_context;
    protected DefaultStyledDocument m_doc;
    private   MutableAttributeSet keyAttr,normalAttr;
    private   MutableAttributeSet inputAttributes =
                new RTFEditorKit().getInputAttributes();

 private String[] keyWord={"int","float"};

    public MyTextPane() {
        super();
        m_context = new StyleContext();
        m_doc = new DefaultStyledDocument(m_context);
        this.setDocument(m_doc);

        this.addKeyListener(new KeyAdapter() {
            public void keyReleased(KeyEvent ke) {
                syntaxParse();
            }
        });

//定义关键字显示属性
        keyAttr = new SimpleAttributeSet();
        StyleConstants.setForeground(keyAttr, Color.green);

//定义一般文本显示属性
        normalAttr = new SimpleAttributeSet();
        StyleConstants.setForeground(normalAttr, Color.blue);
    }

    public void syntaxParse() {
        try {
            String s = null;
            Element root = m_doc.getDefaultRootElement();

            int cursorPos = this.getCaretPosition();   
            int line = root.getElementIndex(cursorPos);

            Element para = root.getElement(line);
            int start = para.getStartOffset();
            int end = para.getEndOffset() - 1;
            s = m_doc.getText(start, end - start);

            int i = 0;
            int xStart = 0;

//分析关键字---
            m_doc.setCharacterAttributes(start, s.length(),normalAttr, false);
            MyStringTokenizer st = new MyStringTokenizer(s);
            while( st.hasMoreTokens()) {
                s = st.nextToken();
                if ( s == null) return;
                for (i = 0; i < keyWord.length; i++ ) {
                    if (s.equals(keyWord[i])) break;
                }
                if ( i >= keyWord.length ) continue;

                xStart = st.getCurrPosition();

                //设置关键字显示属性
                m_doc.setCharacterAttributes(start+xStart, s.length(),
                                             keyAttr, false);
            }
            inputAttributes.addAttributes(normalAttr);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("test text pane");
        frame.getContentPane().add(new MyTextPane());
        WindowListener wndCloser = new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        };
        frame.addWindowListener(wndCloser);
        final int inset = 50;
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
        frame.setBounds ( inset, inset, screenSize.width - inset*2, screenSize.height - inset*2 );
        frame.show();
    }
}

/*在分析字符串的同时，记录每个token所在的位置
*
*/
class MyStringTokenizer extends StringTokenizer{
    String sval = " ";
    String oldStr,str;
    int m_currPosition = 0,m_beginPosition=0;
    MyStringTokenizer(String str) {
        super(str," ");
        this.oldStr = str;
        this.str = str;
    }

    public String nextToken() {
       try {
           String s = super.nextToken();
           int pos = -1;

           if (oldStr.equals(s)) {
               return s;
           }

           pos = str.indexOf(s + sval);
           if ( pos == -1) {
               pos = str.indexOf(sval + s);
               if ( pos == -1)
                   return null;
               else pos += 1;
           }

           int xBegin = pos + s.length();
           str = str.substring(xBegin);

           m_currPosition = m_beginPosition + pos;
           m_beginPosition = m_beginPosition + xBegin;
           return s;
       } catch (java.util.NoSuchElementException ex) {
           ex.printStackTrace();
           return null;
       }
    }

   //返回token在字符串中的位置
   public int getCurrPosition() {
       return m_currPosition;
   }
}