code: public void cancel(long id) {
  
  		// Lookup the background call for the given id.
  		Caller cancel = backgroundCalls.get(id);
  		if(cancel == null) {
  			return;
  		}
  
  		// Cancel the thread
  		cancel.cancel();
  
  		try {
  			// Wait for the thread
  			cancel.join();
  		} catch (InterruptedException ex) {
  			// Ignore this
  		}
  
  	}
docs: Cancel a specific asynchronous call.
  
  @param id The id of the call as returned by the callAsync method.