question: protected void start ( ) { checkState ( executorService == null , "Cannot restart a Model" ) ; executorService = Executors . newSingleThreadExecutor ( ) ; requestQueue = new SynchronousQueue < GenerationRequest > ( ) ; CompilerRunner compilerRunner = new CompilerRunner ( ) ; executorService . execute ( compilerRunner ) ; processingEnv = compilerRunner . getProcessingEnvironment ( ) ; }
target:  Starts up the compiler thread and waits for it to return the processing environment. 