question: public Future < ? > execute ( CameraCommand command ) { if ( mClosed ) { return Futures . immediateFuture ( null ) ; } synchronized ( mLock ) { if ( mExecutor == null ) { mExecutor = mExecutorProvider . get ( ) ; } checkNotNull ( mExecutor ) ; return mExecutor . submit ( new CommandRunnable ( command ) ) ; } }
target:  Executes the given command, returning a Future to indicate its status and allow (interruptible) cancellation.