question: @ CallerSensitive public static < U , W > AtomicReferenceFieldUpdater < U , W > newUpdater ( Class < U > tclass , Class < W > vclass , String fieldName ) { return new AtomicReferenceFieldUpdaterImpl < U , W > ( tclass , vclass , fieldName , Reflection . getCallerClass ( ) ) ; }
target:  Creates and returns an updater for objects with the given field. The Class arguments are needed to check that reflective types and generic types match.