code: public static HttpURLConnection clearMessages(final URI uri, final QueueRequestOptions queueOptions,
              final OperationContext opContext) throws URISyntaxException, IOException, StorageException {
          return BaseRequest.delete(uri, queueOptions, null, opContext);
      }
docs: Constructs a web request to clear all the messages in the queue. Sign the
  web request with a length of -1L.
  
  @param uri
  A <code>URI</code> object that specifies the absolute URI to
  the queue.
  @param queueOptions
  A {@link QueueRequestOptions} object that specifies execution options such as retry policy and timeout
  settings for the operation. Specify <code>null</code> to use the request options specified on the
  {@link CloudQueueClient}.
  @param opContext
  An {@link OperationContext} object that represents the context
  for the current operation. This object is used to track
  requests to the storage service, and to provide additional
  runtime information about the operation.
  
  @return An <code>HttpURLConnection</code> configured for the specified
  operation.
  
  @throws IOException
  @throws URISyntaxException
  If the URI is not valid.
  @throws StorageException
  If a storage service error occurred during the operation.