車輪の再発明(確信)

同期ループ.java

import java.util.Iterator;

import lombok.Value;

public class PairCollectionSupport {
	@Value
	public static class Pair<A, B> {
		private A a;
		private B b;
	}

	@Value(staticConstructor = "of")
	public static class PairCollection<A, B> implements Iterable<Pair<? extends A, ? extends B>> {
		private class IteratorImpl implements Iterator<Pair<? extends A, ? extends B>> {
			private Iterator<? extends A> asIterator;
			private Iterator<? extends B> bsIterator;

			@Override
			public boolean hasNext() {
				boolean hasNextA = asIterator.hasNext();
				boolean hasNextB = bsIterator.hasNext();
				boolean hasDiff = hasNextA != hasNextB;
				if (hasDiff && !ignoreOveredLength) {
					throw new ArrayIndexOutOfBoundsException(String.format("different length iterators."));
				}
				return asIterator.hasNext() && bsIterator.hasNext();
			}

			@Override
			public Pair<? extends A, ? extends B> next() {
				return new Pair<>(asIterator.next(), bsIterator.next());
			}

			@Override
			public void remove() {
				asIterator.remove();
				bsIterator.remove();
			}
		}

		private Iterable<? extends A> as;

		private Iterable<? extends B> bs;

		private boolean ignoreOveredLength;

		public PairCollection(Iterable<? extends A> as, Iterable<? extends B> bs) {
			this(as, bs, true);
		}

		public PairCollection(Iterable<? extends A> as, Iterable<? extends B> bs, boolean ignoreOveredLength) {
			super();
			this.as = as;
			this.bs = bs;
			this.ignoreOveredLength = ignoreOveredLength;
		}

		@Override
		public Iterator<Pair<? extends A, ? extends B>> iterator() {
			return new IteratorImpl();
		}
	}
}