[YouTube-API] InvalidEntryException while connecting

I successfully compiled YouTubeReadonlyClient.java from Google Data
APIs Client Library, but I got error running it.

Console is next:

The server had a problem handling your request.
com.google.gdata.util.InvalidEntryException: Invalid value for
parameter: username
<errors xmlns='http://schemas.google.com/g/2005'><error><domain>GData</
domain><code>InvalidRequestUriException</code><internalReason>Invalid
value for parameter: username</internalReason></error></errors>
at
com.google.gdata.client.http.HttpGDataRequest.handleErrorResponse(HttpGDataRequest.java:
602)
at
com.google.gdata.client.http.GoogleGDataRequest.handleErrorResponse(GoogleGDataRequest.java:
564)
at
com.google.gdata.client.http.HttpGDataRequest.checkResponse(HttpGDataRequest.java:
560)
at
com.google.gdata.client.http.HttpGDataRequest.execute(HttpGDataRequest.java:
538)
at
com.google.gdata.client.http.GoogleGDataRequest.execute(GoogleGDataRequest.java:
536)
at com.google.gdata.client.Service.getFeed(Service.java:1135)
at com.google.gdata.client.Service.getFeed(Service.java:998)
at com.google.gdata.client.GoogleService.getFeed(GoogleService.java:
645)
at com.google.gdata.client.Service.getFeed(Service.java:1017)
at
sample.youtube.YouTubeReadonlyClient.printVideoFeed(YouTubeReadonlyClient.java:
545)
at
sample.youtube.YouTubeReadonlyClient.printUploads(YouTubeReadonlyClient.java:
508)
at
sample.youtube.YouTubeReadonlyClient.main(YouTubeReadonlyClient.java:
735)

Why is this?

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