code: public static <T, U> Collector<T, ?, Integer> bitOrInt(ToIntFunction<? super T> function) {
          return Collector.of(() -> new int[1],
              (s, v) -> {
                  s[0] = s[0] | function.applyAsInt(v);
              },
              (s1, s2) -> {
                  s1[0] = s1[0] | s2[0];
                  return s1;
              },
              s -> s[0]
          );
      }
docs: Get a {@link Collector} that calculates the <code>BIT_OR()</code> for any
  type of {@link Number}.