rishabhdaim commented on code in PR #2055: URL: https://github.com/apache/jackrabbit-oak/pull/2055#discussion_r1959058008
########## oak-commons/src/main/java/org/apache/jackrabbit/oak/commons/collections/IterableUtils.java: ########## @@ -0,0 +1,145 @@ +/* + * 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.jackrabbit.oak.commons.collections; + +import org.apache.commons.collections4.iterators.LazyIteratorChain; + +import java.util.Iterator; +import java.util.Objects; + +/** + * Utility methods for {@link Iterable} conversions. + */ +public class IterableUtils { + + private IterableUtils() { + // no instances for you + } + + /** + * Combines two iterables into a single iterable. + * <p> + * The returned iterable has an iterator that traverses the elements in {@code a}, + * followed by the elements in {@code b}. The source iterators are not polled until necessary. + * <p> + * The returned iterable's iterator supports {@code remove()} when the corresponding + * input iterator supports it. + * + * @param <E> the element type + * @param a the first iterable, may not be null + * @param b the second iterable, may not be null + * @return a new iterable, combining the provided iterables + * @throws NullPointerException if either of the provided iterables is null + */ + public static <E> Iterable<E> chainedIterable(final Iterable<? extends E> a, + final Iterable<? extends E> b) { + return org.apache.commons.collections4.IterableUtils.chainedIterable(a, b); + } + + /** + * Combines three iterables into a single iterable. + * <p> + * The returned iterable has an iterator that traverses the elements in {@code a}, + * followed by the elements in {@code b} and {@code c}. The source + * iterators are not polled until necessary. + * <p> + * The returned iterable's iterator supports {@code remove()} when the corresponding + * input iterator supports it. + * + * @param <E> the element type + * @param a the first iterable, may not be null + * @param b the second iterable, may not be null + * @param c the third iterable, may not be null + * @return a new iterable, combining the provided iterables + * @throws NullPointerException if either of the provided iterables is null + */ + public static <E> Iterable<E> chainedIterable(final Iterable<? extends E> a, + final Iterable<? extends E> b, + final Iterable<? extends E> c) { + return org.apache.commons.collections4.IterableUtils.chainedIterable(a, b, c); + } + + /** + * Combines four iterables into a single iterable. + * <p> + * The returned iterable has an iterator that traverses the elements in {@code a}, + * followed by the elements in {@code b}, {@code c} and {@code d}. The source + * iterators are not polled until necessary. + * <p> + * The returned iterable's iterator supports {@code remove()} when the corresponding + * input iterator supports it. + * + * @param <E> the element type + * @param a the first iterable, may not be null + * @param b the second iterable, may not be null + * @param c the third iterable, may not be null + * @param d the fourth iterable, may not be null + * @return a new iterable, combining the provided iterables + * @throws NullPointerException if either of the provided iterables is null + */ + public static <E> Iterable<E> chainedIterable(final Iterable<? extends E> a, + final Iterable<? extends E> b, + final Iterable<? extends E> c, + final Iterable<? extends E> d) { + return org.apache.commons.collections4.IterableUtils.chainedIterable(a, b, c, d); + } + + /** + * Combines the provided iterables into a single iterable. + * <p> + * The returned iterable has an iterator that traverses the elements in the order + * of the arguments, i.e. iterables[0], iterables[1], .... The source iterators + * are not polled until necessary. + * <p> + * The returned iterable's iterator supports {@code remove()} when the corresponding + * input iterator supports it. + * + * @param <E> the element type + * @param iterables the iterables to combine, may not be null + * @return a new iterable, combining the provided iterables + * @throws NullPointerException if either of the provided iterables is null + */ + @SafeVarargs + public static <E> Iterable<E> chainedIterable(final Iterable<? extends E>... iterables) { + Objects.requireNonNull(iterables); + return org.apache.commons.collections4.IterableUtils.chainedIterable(iterables); + } + + /** + * Creates an {@code Iterable} that chains multiple {@code Iterable} instances into a single {@code Iterable}. + * <p> + * The returned {@code Iterable} will iterate over all elements of the first {@code Iterable}, + * then all elements of the second, and so on. + * + * @param <E> the type of elements returned by the iterator + * @param iterables an {@code Iterable} of {@code Iterable} instances to be chained + * @return an {@code Iterable} that provides a single view of all elements in the input {@code Iterable} instances + * @throws NullPointerException if the input {@code Iterable} or any of its elements are null + */ + public static <E> Iterable<E> chainedIterable(final Iterable<? extends Iterable<? extends E>> iterables) { Review Comment: @thomasmueller yes. This method would be repalcing Guava's **Iterables.concat** [1] and that method is used at many places inside code. [1] https://guava.dev/releases/20.0/api/docs/com/google/common/collect/Iterables.html#concat-java.lang.Iterable- -- 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. To unsubscribe, e-mail: oak-dev-unsubscr...@jackrabbit.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
