"Authorization required" - Error message - from com.google.gdata.util.AuthenticationException

HELP ME, I got problem when trying to create New Spreadsheet using
Spreadsheet API.
1. The first, I make a function to create a new Spreadsheed and insert to
Google DocsService:

public DocumentListEntry createNewDocument(String title)
            throws IOException, ServiceException {
        DocumentListEntry newEntry = null;

        newEntry = new SpreadsheetEntry();

        newEntry.setTitle(new PlainTextConstruct(title));
        return docsService.insert(new URL(
        "http://docs.google.com/feeds/documents/private/full"),
                newEntry);
    }

2. I use Java code below to call function above, to create a new Speadsheet
which I name it "test-thuycq84":
                // declare a new entry  for spreadsheet 
        DocumentListEntry createdEntry = null;

        // Create an empty spreadsheet
        try {
            createdEntry = createNewDocument("test-thuycq84");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ServiceException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        System.out.println("Spreadsheet now online @ :"+
createdEntry.getHtmlLink().getHref());

3. When i run program on Windows XP, expected output that:
"Spreadsheet now online @:<http://...>"

But it returns output with an error as below: 

com.google.gdata.util.AuthenticationException: Authorization required
<HTML>
<HEAD>
<TITLE>Authorization required</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF" TEXT="#000000">
<H1>Authorization required</H1>
<H2>Error 401</H2>
</BODY>
</HTML>

    at
com.google.gdata.client.http.HttpGDataRequest.handleErrorResponse(HttpGDataReque
st.java:508)
    at
com.google.gdata.client.http.GoogleGDataRequest.handleErrorResponse(GoogleGDataR
equest.java:555)
    at
com.google.gdata.client.http.HttpGDataRequest.checkResponse(HttpGDataRequest.jav
a:480)
    at
com.google.gdata.client.http.HttpGDataRequest.execute(HttpGDataRequest.java:459)
    at
com.google.gdata.client.http.GoogleGDataRequest.execute(GoogleGDataRequest.java:
527)
    at com.google.gdata.client.Service.insert(Service.java:1243)
    at com.google.gdata.client.GoogleService.insert(GoogleService.java:560)
    at com.google.gdata.client.media.MediaService.insert(MediaService.java:323)
    at uploadrms.testNewSS.createNewDocument(testNewSS.java:111)
    at uploadrms.testNewSS.init(testNewSS.java:92)
    at uploadrms.testNewSS.main(testNewSS.java:61)

############

What must I do to fix this problem? I need help...!!

Original issue reported on code.google.com by thuyc...@gmail.com on 5 Jan 2010 at 3:30

mmt123 / ga-api-java-samples

"Authorization required" - Error message - from com.google.gdata.util.AuthenticationException #3