code: protected FieldDeclaration declareLongFieldUpdater(String className, String variableName) {
          MethodCallExpr initializer = newAtomicLongFieldUpdater(className, variableName);
  
          ClassOrInterfaceType type = simpleParametricType("AtomicLongFieldUpdater", className);
          FieldDeclaration newField = fieldDeclarationWithInitialiser(type, fieldUpdaterFieldName(variableName),
                  initializer, Modifier.PRIVATE, Modifier.STATIC, Modifier.FINAL);
          return newField;
      }
docs: Generates something like
  <code>private static final AtomicLongFieldUpdater<MpmcAtomicArrayQueueProducerIndexField> P_INDEX_UPDATER = AtomicLongFieldUpdater.newUpdater(MpmcAtomicArrayQueueProducerIndexField.class, "producerIndex");</code>
  
  @param className
  @param variableName
  @return