Speech Recognition: javax.speech.recognition

Hi, I am writing my first speech recognition application using The javax.speech.recognition package
The problem is that Central.availableSynthesizers() and Central.availableRecognizers() always return empty lists. I googled it and it's said that maybe there is no recognizer avilable, I downloaded Microsoft speech SDK5.1. I am running under Windows 7 and the speech recognition built in windows 7 works fine. I don't know why it always return empty list

Code Java:

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public static void main(String args[]) 
{
 
                    EngineList engineList=   Central.availableSynthesizers(null) ;
                  EngineModeDesc desc= new EngineModeDesc(Locale.getDefault()); 
                  EngineList list = Central.availableRecognizers(desc);
}

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Thanks in advance