anantdamle commented on a change in pull request #238: URL: https://github.com/apache/commons-collections/pull/238#discussion_r643575137
########## File path: src/main/java/org/apache/commons/collections4/iterators/PairedIterator.java ########## @@ -0,0 +1,171 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.collections4.iterators; + +import static java.util.Objects.requireNonNull; + +import java.util.Iterator; +import java.util.NoSuchElementException; +import org.apache.commons.collections4.iterators.PairedIterator.PairedItem; + +/** + * Provides a iteration over the elements contained in a pair of Iterators. + * + * <p> + * Given two {@link Iterator} instances {@code A} and {@code B}, the {@link #next} method on this + * iterator provide a Pair of {@code A.next()} and {@code B.next()} until one of the iterators is + * exhausted. + * </p> + * Example usage: + * <pre>{@code + * List<Integer> studentIds = ... + * List<String> studentNames = ... + * + * PairedIterator<PairedItem<Integer, String>> pairedIterator = + * PairedIterator.ofIterables(studentIds, studentNames); + * + * while (pairedIterator.hasNext()) { + * PairedItem<Integer, String> item = zippedIterator.next(); + * ... + * } + * }</pre> + * + * @param <L> the left elements' type + * @param <R> the right elements' type + */ +public class PairedIterator<L, R> implements Iterator<PairedItem<L, R>> { + + /** + * The left {@link Iterator}s to evaluate. + */ + private final Iterator<L> leftIterator; + + /** + * The right {@link Iterator}s to evaluate. + */ + private final Iterator<R> rightIterator; + + // Constructor + // ---------------------------------------------------------------------- + + /** + * Constructs a new {@code ZipPairIterator} that will provide iteration over the two given + * iterators. + * + * @param leftIterator the iterator for the left side element. + * @param rightIterator the iterator for the right side element. + * @throws NullPointerException if either iterator is null + */ + public PairedIterator(Iterator<L> leftIterator, Iterator<R> rightIterator) { + this.leftIterator = requireNonNull(leftIterator); + this.rightIterator = requireNonNull(rightIterator); + } + + /** + * Convenience static factory to construct the ZipPairIterator + * + * @param leftIterator the iterator for the left side element. + * @param rightIterator the iterator for the right side element. + * @return the iterator to iterate over the provided iterators. + * @throws NullPointerException if either iterator is null + */ + public static <L, R> PairedIterator<L, R> of(Iterator<L> leftIterator, Iterator<R> rightIterator) { + return new PairedIterator<>(leftIterator, rightIterator); + } + + /** + * Convenience static factory to construct the ZipPairIterator from any {@link Iterable} sources. + * + * @param leftIterable the iterable for the left side element. + * @param rightIterable the iterable for the right side element. + * @return the iterator to iterate over the iterators derived from the provided iterables. + * @throws NullPointerException if either iterables is null + */ + public static <L, R> PairedIterator<L, R> ofIterables(Iterable<L> leftIterable, Iterable<R> rightIterable) { + return of(requireNonNull(leftIterable).iterator(), requireNonNull(rightIterable).iterator()); + } + + // Iterator Methods + // ------------------------------------------------------------------- + + /** + * Returns {@code true} if both the child iterators have remaining elements. + * + * @return true if both the child iterators have remaining elements + */ + @Override + public boolean hasNext() { + return leftIterator.hasNext() && rightIterator.hasNext(); + } + + /** + * Returns the next elements from both the child iterators. + * + * @return the next elements from both the iterators. + * @throws NoSuchElementException if any one child iterator is exhausted. + */ + @Override + public PairedItem<L, R> next() { + if (!hasNext()) { + throw new NoSuchElementException(); + } + + return PairedItem.of(leftIterator.next(), rightIterator.next()); + } + + /** + * An immutable tuple class to represent elements from both the iterators. + * + * @param <L> the left elements' type + * @param <R> the right elements' type + */ Review comment: I usually use `ImmutablePair`, but that is in apache/commons-lang3 , that is not a dependency in this project and didn't think should add, but open to ideas. If you point me to a Pair Class, would be open to using an existing pair class. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
