How to write The query?

for example,I want to query UAL950 which specified planes by Java google-gson parsing in firhose_documentation,then the query should be how to write?
“live filter ??? username james password 123456”
How to write this query?

Firehose is not appropriate for monitoring only a single flight. It is intended for bulk monitoring of all global flights simultaneously.

If you need to monitor only a single flight, then you should use the FlightXML SOAP or REST interface. The FlightInfoEx function will probably be your starting point.