JavaのStreamにもLINQみたいな機能が欲しかった

StreamHelper.java

import lombok.AccessLevel;
import lombok.AllArgsConstructor;
import lombok.NonNull;

import java.util.Iterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

public final class StreamHelper {
    public static <T, U, R> Stream<R> zip(@NonNull Stream<T> s1, @NonNull Stream<U> s2, @NonNull BiFunction<T, U, R> mapper, int size) {
        PairIterator<T, U, R> itr = new PairIterator<>(s1.iterator(), s2.iterator(), mapper);
        int characteristics = Spliterator.IMMUTABLE | Spliterator.NONNULL;
        if (size < 0) {
            return StreamSupport.stream(
                    Spliterators.spliteratorUnknownSize(itr, characteristics), false);
        } else {
            return StreamSupport.stream(
                    Spliterators.spliterator(itr, size, characteristics), false);
        }
    }

    public static <T, U, R> Stream<R> zip(@NonNull Stream<T> s1, @NonNull Stream<U> s2, @NonNull BiFunction<T, U, R> mapper) {
        return zip(s1, s2, mapper, -1);
    }

    @AllArgsConstructor(access = AccessLevel.PRIVATE)
    private static class PairIterator<T, U, R> implements Iterator<R> {
        private final Iterator<T> i1;
        private final Iterator<U> i2;
        private final BiFunction<T, U, R> mapper;

        @Override
        public boolean hasNext() {
            return i1.hasNext() && i2.hasNext();
        }

        @Override
        public R next() {
            return mapper.apply(i1.next(), i2.next());
        }
    }
}