AbstractIterator<Integer> empty =
        new AbstractIterator<Integer>() {
          private boolean alreadyCalledEndOfData;

          @Override
          public @Nullable Integer computeNext() {
            if (alreadyCalledEndOfData) {
              fail("Should not have been invoked again");
            }
            alreadyCalledEndOfData = true;
            return endOfData();
          }
        };

    try {

    AbstractIterator<Integer> empty =
        new AbstractIterator<Integer>() {
          private boolean alreadyCalledEndOfData;

          @Override
          public @Nullable Integer computeNext() {
            if (alreadyCalledEndOfData) {
              fail("Should not have been invoked again");
            }
            alreadyCalledEndOfData = true;
            return endOfData();
          }
        };

    try {