Method forEach

guava/src/com/google/common/collect/Iterables.java:583–592

(Consumer<? super T> action)

      }

      @Override
      public void forEach(Consumer<? super T> action) {
        checkNotNull(action);
        unfiltered.forEach(
            (@ParametricNullness T a) -> {
              if (retainIfTrue.test(a)) {
                action.accept(a);
              }
            });
      }

      @Override
      @GwtIncompatible // Spliterator