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Posted to issues@commons.apache.org by GitBox <gi...@apache.org> on 2021/06/01 19:42:32 UTC
[GitHub] [commons-collections] garydgregory commented on a change in pull request #238: [COLLECTIONS-795] Add a new Iterator to allowing zipping over two iterators of different types
garydgregory commented on a change in pull request #238:
URL: https://github.com/apache/commons-collections/pull/238#discussion_r643425608
##########
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:
We need to think about this because Common Lang already defines different kinds of Pair classes...
##########
File path: src/test/java/org/apache/commons/collections4/iterators/PairedIteratorTest.java
##########
@@ -0,0 +1,150 @@
+/*
+ * 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 java.util.ArrayList;
+import java.util.Iterator;
+import java.util.Random;
+import java.util.UUID;
+import org.apache.commons.collections4.IteratorUtils;
+import org.apache.commons.collections4.iterators.PairedIterator.PairedItem;
+
+
+/** Unit test suite for {@link ZippingIterator}. */
+public final class PairedIteratorTest
+ extends AbstractIteratorTest<PairedItem<String, Integer>> {
+
+ //------------------------------------------------------------ Conventional
+
+ public PairedIteratorTest(String testName) {
+ super(testName);
+ }
+
+ //------------------------------------------------------------ Lifecycle
+
+ private ArrayList<String> smallStringsList = null;
+ private ArrayList<String> largeStringsList = null;
+ private ArrayList<Integer> smallIntsList = null;
+ private ArrayList<Integer> largeIntsList = null;
+
+ // Unequal sized lists
+ private static final int SMALL_LIST_SIZE = 20;
Review comment:
If you expect the sizes to be different, you should assert that fact somewhere.
##########
File path: src/main/java/org/apache/commons/collections4/IteratorUtils.java
##########
@@ -907,6 +908,20 @@ public static NodeListIterator nodeListIterator(final Node node) {
return new ZippingIterator<>(iterators);
}
+ /**
+ * Returns an iterator that provides the elements contained in a pair of Iterators.
+ *
+ * @param <L> the left elements' type
+ * @param <R> the right elements' type
+ * @param left the iterator for the left side elements
+ * @param right the iterator for the right side elements
+ * @return an iterator, to iterate over the decorated iterators together until one is exhausted
+ * @throws NullPointerException if any iterator is null
Review comment:
All new public and protected methods should have a Javadoc since 4.5 tag.
##########
File path: src/test/java/org/apache/commons/collections4/PairedIterableTest.java
##########
@@ -0,0 +1,84 @@
+/*
+ * 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;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.Random;
+import java.util.UUID;
+import java.util.stream.Collectors;
+import org.apache.commons.collections4.iterators.PairedIterator.PairedItem;
+import org.junit.Before;
+import org.junit.Test;
+
+public final class PairedIterableTest {
+ private ArrayList<String> smallStringsList = null;
Review comment:
Don't override default vslues with default values.
##########
File path: src/test/java/org/apache/commons/collections4/iterators/PairedIteratorTest.java
##########
@@ -0,0 +1,150 @@
+/*
+ * 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 java.util.ArrayList;
+import java.util.Iterator;
+import java.util.Random;
+import java.util.UUID;
+import org.apache.commons.collections4.IteratorUtils;
+import org.apache.commons.collections4.iterators.PairedIterator.PairedItem;
+
+
+/** Unit test suite for {@link ZippingIterator}. */
+public final class PairedIteratorTest
+ extends AbstractIteratorTest<PairedItem<String, Integer>> {
+
+ //------------------------------------------------------------ Conventional
Review comment:
No need for these inline comments, they document nothing.
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