Java XPath evaluate() problem

import javax.xml.xpath.*;
import org.xml.sax.InputSource;
import java.io.StringReader;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
 
public class EvaluateTest {
 
   /**
    * @param args
    */
   public static void main(String[] args) {
      String myxml = "<?xml version='1.0' encoding='utf-8' ?><mytest><ChannelList>" + 
	             "<Channel><ChannelId>0001</ChannelId><ChannelName>Ch1</ChannelName></Channel>" +
                             "<Channel><ChannelId>0002</ChannelId><ChannelName>Ch2</ChannelName></Channel>" +
	             "<Channel><ChannelId>0003</ChannelId><ChannelName>Ch3</ChannelName></Channel>" +
	             "</ChannelList></mytest>";
			
      //Get the Document object
      Document doc = null;
      try {
            InputSource inputSource = new InputSource();
            inputSource.setCharacterStream( new StringReader(myxml));
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder db = factory.newDocumentBuilder();
            doc = db.parse(inputSource);
					
            //Iterate thru the Channel list 
            NodeList channellist = getSubElements(doc, "/mytest/ChannelList/Channel");
            if (channellist==null)
                  System.out.println("the channel list is null");
		
            for (int i=0, len=channellist.getLength(); i<len; i++) {
                  System.out.println("Channel #" + i);
				
                  String name = getTagValue(channellist.item(i), "//ChannelName/text()", -1);
                  System.out.println("Channel Name : " + name);
            }
      } catch ( Exception e ) {
            e.printStackTrace();
            return;
      }
   }
	
	
   //Get the text value of a tag from a document object using XPath method
   static public String getTagValue(Object doc, String xpathstr, int index) throws Exception {
      String result = "";
		
      if ((doc==null)	|| (xpathstr==null) || "".equals(xpathstr)) 
            return result;
		
      XPathFactory factory = XPathFactory.newInstance();
      XPath xpath = factory.newXPath();
      result = (String)xpath.evaluate(xpathstr, doc, XPathConstants.STRING);
      if (result==null)
            result = "";
		
      return result;
   }
	
	
   static public NodeList getSubElements(Object doc, String xpathstr) throws Exception {
      if ((doc==null)	|| (xpathstr==null) || "".equals(xpathstr)) 
            return null;
		
      XPathFactory factory = XPathFactory.newInstance();
      XPath xpath = factory.newXPath();
      Object result = xpath.evaluate(xpathstr, doc, XPathConstants.NODESET);
      return (NodeList)result;
   }
 
}

                                  

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:
46:
47:
48:
49:
50:
51:
52:
53:
54:
55:
56:
57:
58:
59:
60:
61:
62:
63:
64:
65:
66:
67:
68:
69:
70:
71:
72:
73:
74:
75: