| /* |
| * 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 java.util.Arrays; |
| import java.util.Collection; |
| import java.util.Comparator; |
| import java.util.Enumeration; |
| import java.util.Iterator; |
| import java.util.List; |
| |
| import org.apache.commons.collections4.iterators.SingletonIterator; |
| |
| /** |
| * A FluentIterable provides a powerful yet simple API for manipulating |
| * Iterable instances in a fluent manner. |
| * <p> |
| * A FluentIterable can be created either from an Iterable or from a set |
| * of elements. The following types of methods are provided: |
| * <ul> |
| * <li>fluent methods which return a new {@code FluentIterable} instance, |
| * providing a view of the original iterable (e.g. filter(Predicate)); |
| * <li>conversion methods which copy the FluentIterable's contents into a |
| * new collection or array (e.g. toList()); |
| * <li>utility methods which answer questions about the FluentIterable's |
| * contents (e.g. size(), anyMatch(Predicate)). |
| * <li> |
| * </ul> |
| * <p> |
| * The following example outputs the first 3 even numbers in the range [1, 10] |
| * into a list: |
| * <pre> |
| * List<String> result = |
| * FluentIterable |
| * .of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) |
| * .filter(new Predicate<Integer>() { |
| * public boolean evaluate(Integer number) { |
| * return number % 2 == 0; |
| * } |
| * ) |
| * .transform(TransformerUtils.stringValueTransformer()) |
| * .limit(3) |
| * .toList(); |
| * </pre> |
| * The resulting list will contain the following elements: |
| * <pre>[2, 4, 6]</pre> |
| * |
| * @param <E> the element type |
| * @since 4.1 |
| * @version $Id$ |
| */ |
| public class FluentIterable<E> implements Iterable<E> { |
| |
| /** A reference to the wrapped iterable. */ |
| private final Iterable<E> iterable; |
| |
| // Static factory methods |
| // ---------------------------------------------------------------------- |
| |
| /** |
| * Creates a new empty FluentIterable. |
| * |
| * @param <T> the element type |
| * @return a new empty FluentIterable |
| */ |
| @SuppressWarnings("unchecked") |
| public static <T> FluentIterable<T> empty() { |
| return IterableUtils.EMPTY_ITERABLE; |
| } |
| |
| /** |
| * Creates a new FluentIterable of the single provided element. |
| * <p> |
| * The returned iterable's iterator does not support {@code remove()}. |
| * |
| * @param <T> the element type |
| * @param singleton the singleton element |
| * @return a new FluentIterable containing the singleton |
| */ |
| public static <T> FluentIterable<T> of(final T singleton) { |
| return of(IteratorUtils.asIterable(new SingletonIterator<T>(singleton, false))); |
| } |
| |
| /** |
| * Creates a new FluentIterable from the provided elements. |
| * <p> |
| * The returned iterable's iterator does not support {@code remove()}. |
| * |
| * @param <T> the element type |
| * @param elements the elements to be contained in the FluentIterable |
| * @return a new FluentIterable containing the provided elements |
| */ |
| public static <T> FluentIterable<T> of(final T... elements) { |
| return of(Arrays.asList(elements)); |
| } |
| |
| /** |
| * Construct a new FluentIterable from the provided iterable. If the |
| * iterable is already an instance of FluentIterable, the instance |
| * will be returned instead. |
| * <p> |
| * The returned iterable's iterator supports {@code remove()} when the |
| * corresponding input iterator supports it. |
| * |
| * @param <T> the element type |
| * @param iterable the iterable to wrap into a FluentIterable, may not be null |
| * @return a new FluentIterable wrapping the provided iterable |
| * @throws NullPointerException if iterable is null |
| */ |
| public static <T> FluentIterable<T> of(final Iterable<T> iterable) { |
| IterableUtils.checkNotNull(iterable); |
| if (iterable instanceof FluentIterable<?>) { |
| return (FluentIterable<T>) iterable; |
| } else { |
| return new FluentIterable<T>(iterable); |
| } |
| } |
| |
| // Constructor |
| // ---------------------------------------------------------------------- |
| |
| /** |
| * Package-private constructor, used by IterableUtils. |
| */ |
| FluentIterable() { |
| this.iterable = this; |
| } |
| |
| /** |
| * Create a new FluentIterable by wrapping the provided iterable. |
| * @param iterable the iterable to wrap |
| */ |
| private FluentIterable(final Iterable<E> iterable) { |
| this.iterable = iterable; |
| } |
| |
| // fluent construction methods |
| // ---------------------------------------------------------------------- |
| |
| /** |
| * Returns a new FluentIterable whose iterator will first traverse |
| * the elements of the current iterable, followed by the provided |
| * elements. |
| * |
| * @param elements the elements to append to the iterable |
| * @return a new iterable, combining this iterable with the elements |
| */ |
| public FluentIterable<E> append(final E... elements) { |
| return append(Arrays.asList(elements)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will first traverse |
| * the elements of the current iterable, followed by the elements |
| * of the provided iterable. |
| * |
| * @param other the other iterable to combine, may not be null |
| * @return a new iterable, combining this iterable with other |
| * @throws NullPointerException if other is null |
| */ |
| public FluentIterable<E> append(final Iterable<? extends E> other) { |
| return of(IterableUtils.chainedIterable(iterable, other)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will traverse the |
| * elements of the current and provided iterable in natural order. |
| * <p> |
| * Example: natural ordering |
| * <ul> |
| * <li>this contains elements [1, 3, 5, 7] |
| * <li>other contains elements [2, 4, 6, 8] |
| * </ul> |
| * <p> |
| * The returned iterable will traverse the elements in the following |
| * order: [1, 2, 3, 4, 5, 6, 7, 8] |
| * |
| * @param other the other iterable to collate, may not be null |
| * @return a new iterable, collating this iterable with the other in natural order |
| * @throws NullPointerException if other is null |
| * @see {@link org.apache.commons.collections4.iterators.CollatingIterator CollatingIterator} |
| */ |
| public FluentIterable<E> collate(final Iterable<? extends E> other) { |
| return of(IterableUtils.collatedIterable(iterable, other)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will traverse the |
| * elements of the current and provided iterable according to the |
| * ordering defined by an comparator. |
| * <p> |
| * Example: descending order |
| * <ul> |
| * <li>this contains elements [7, 5, 3, 1] |
| * <li>other contains elements [8, 6, 4, 2] |
| * </ul> |
| * <p> |
| * The returned iterable will traverse the elements in the following |
| * order: [8, 7, 6, 5, 4, 3, 2, 1] |
| * |
| * @param comparator the comparator to define an ordering, may be null, |
| * in which case natural ordering will be used |
| * @param other the other iterable to collate, may not be null |
| * @return a new iterable, collating this iterable with the other in natural order |
| * @throws NullPointerException if other is null |
| * @see {@link org.apache.commons.collections4.iterators.CollatingIterator CollatingIterator} |
| */ |
| public FluentIterable<E> collate(final Iterable<? extends E> other, |
| final Comparator<? super E> comparator) { |
| return of(IterableUtils.collatedIterable(comparator, iterable, other)); |
| } |
| |
| /** |
| * This method fully traverses an iterator of this iterable and returns |
| * a new iterable with the same contents, but without any reference |
| * to the originating iterables and/or iterators. |
| * <p> |
| * Calling this method is equivalent to: |
| * <pre> |
| * FluentIterable<E> someIterable = ...; |
| * FluentIterable.of(someIterable.toList()); |
| * </pre> |
| * |
| * @return a new iterable with the same contents as this iterable |
| */ |
| public FluentIterable<E> eval() { |
| return of(toList()); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will only return |
| * elements from this iterable matching the provided predicate. |
| * |
| * @param predicate the predicate used to filter elements |
| * @return a new iterable, providing a filtered view of this iterable |
| * @throws NullPointerException if predicate is null |
| */ |
| public FluentIterable<E> filter(final Predicate<? super E> predicate) { |
| return of(IterableUtils.filteredIterable(iterable, predicate)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will return at most |
| * the provided maximum number of elements from this iterable. |
| * |
| * @param maxSize the maximum number of elements |
| * @return a new iterable, providing a bounded view of this iterable |
| * @throws IllegalArgumentException if maxSize is negative |
| */ |
| public FluentIterable<E> limit(final long maxSize) { |
| return of(IterableUtils.boundedIterable(iterable, maxSize)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will loop infinitely |
| * over the elements from this iterable. |
| * |
| * @return a new iterable, providing a looping view of this iterable |
| */ |
| public FluentIterable<E> loop() { |
| return of(IterableUtils.loopingIterable(iterable)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will traverse the |
| * elements from this iterable in reverse order. |
| * |
| * @return a new iterable, providing a reversed view of this iterable |
| */ |
| public FluentIterable<E> reverse() { |
| return of(IterableUtils.reversedIterable(iterable)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will skip the first |
| * N elements from this iterable. |
| * |
| * @param elementsToSkip the number of elements to skip |
| * @return a new iterable, providing a view of this iterable by skipping |
| * the first N elements |
| * @throws IllegalArgumentException if elementsToSkip is negative |
| */ |
| public FluentIterable<E> skip(final long elementsToSkip) { |
| return of(IterableUtils.skippingIterable(iterable, elementsToSkip)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will return all elements |
| * of this iterable transformed by the provided transformer. |
| * |
| * @param <O> the output element type |
| * @param transformer the transformer applied to each element |
| * @return a new iterable, providing a transformed view of this iterable |
| * @throws NullPointerException if transformer is null |
| */ |
| public <O> FluentIterable<O> transform(final Transformer<? super E, ? extends O> transformer) { |
| return of(IterableUtils.transformedIterable(iterable, transformer)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will return a unique view |
| * of this iterable. |
| * |
| * @return a new iterable, providing a unique view of this iterable |
| */ |
| public FluentIterable<E> unique() { |
| return of(IterableUtils.uniqueIterable(iterable)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will return an unmodifiable |
| * view of this iterable. |
| * |
| * @return a new iterable, providing an unmodifiable view of this iterable |
| */ |
| public FluentIterable<E> unmodifiable() { |
| return of(IterableUtils.unmodifiableIterable(iterable)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will traverse |
| * the elements of this iterable and the other iterable in |
| * alternating order. |
| * |
| * @param other the other iterable to interleave, may not be null |
| * @return a new iterable, interleaving this iterable with others |
| * @throws NullPointerException if other is null |
| */ |
| public FluentIterable<E> zip(final Iterable<? extends E> other) { |
| return of(IterableUtils.zippingIterable(iterable, other)); |
| } |
| |
| /** |
| * Returns a new FluentIterable whose iterator will traverse |
| * the elements of this iterable and the other iterables in |
| * alternating order. |
| * |
| * @param others the iterables to interleave, may not be null |
| * @return a new iterable, interleaving this iterable with others |
| * @throws NullPointerException if either of the provided iterables is null |
| */ |
| public FluentIterable<E> zip(final Iterable<? extends E>... others) { |
| return of(IterableUtils.zippingIterable(iterable, others)); |
| } |
| |
| // convenience methods |
| // ---------------------------------------------------------------------- |
| |
| /** {@inheritDoc} */ |
| @Override |
| public Iterator<E> iterator() { |
| return iterable.iterator(); |
| } |
| |
| /** |
| * Returns an Enumeration that will enumerate all elements contained |
| * in this iterable. |
| * |
| * @return an Enumeration over the elements of this iterable |
| */ |
| public Enumeration<E> asEnumeration() { |
| return IteratorUtils.asEnumeration(iterator()); |
| } |
| |
| /** |
| * Checks if all elements contained in this iterable are matching the |
| * provided predicate. |
| * <p> |
| * A <code>null</code> or empty iterable returns true. |
| * |
| * @param predicate the predicate to use, may not be null |
| * @return true if all elements contained in this iterable match the predicate, |
| * false otherwise |
| * @throws NullPointerException if predicate is null |
| */ |
| public boolean allMatch(final Predicate<? super E> predicate) { |
| return IterableUtils.matchesAll(iterable, predicate); |
| } |
| |
| /** |
| * Checks if this iterable contains any element matching the provided predicate. |
| * <p> |
| * A <code>null</code> or empty iterable returns false. |
| * |
| * @param predicate the predicate to use, may not be null |
| * @return true if at least one element contained in this iterable matches the predicate, |
| * false otherwise |
| * @throws NullPointerException if predicate is null |
| */ |
| public boolean anyMatch(final Predicate<? super E> predicate) { |
| return IterableUtils.matchesAny(iterable, predicate); |
| } |
| |
| /** |
| * Checks if this iterable is empty. |
| * |
| * @return true if this iterable does not contain any elements, false otherwise |
| */ |
| public boolean isEmpty() { |
| return IterableUtils.isEmpty(iterable); |
| } |
| |
| /** |
| * Checks if the object is contained in this iterable. |
| * |
| * @param object the object to check |
| * @return true if the object is contained in this iterable, false otherwise |
| */ |
| public boolean contains(final Object object) { |
| return IterableUtils.contains(iterable, object); |
| } |
| |
| /** |
| * Applies the closure to all elements contained in this iterable. |
| * |
| * @param closure the closure to apply to each element, may not be null |
| * @throws NullPointerException if closure is null |
| */ |
| public void forEach(final Closure<? super E> closure) { |
| IterableUtils.forEach(iterable, closure); |
| } |
| |
| /** |
| * Returns the element at the provided position in this iterable. |
| * In order to return the element, an iterator needs to be traversed |
| * up to the requested position. |
| * |
| * @param position the position of the element to return |
| * @return the element |
| * @throws IndexOutOfBoundsException if the provided position is outside the |
| * valid range of this iterable: [0, size) |
| */ |
| public E get(final int position) { |
| return IterableUtils.get(iterable, position); |
| } |
| |
| /** |
| * Returns the number of elements that are contained in this iterable. |
| * In order to determine the size, an iterator needs to be traversed. |
| * |
| * @return the size of this iterable |
| */ |
| public int size() { |
| return IterableUtils.size(iterable); |
| } |
| |
| /** |
| * Traverses an iterator of this iterable and adds all elements |
| * to the provided collection. |
| * |
| * @param collection the collection to add the elements |
| * @throws NullPointerException if collection is null |
| */ |
| public void copyInto(final Collection<? super E> collection) { |
| if (collection == null) { |
| throw new NullPointerException("Collection must not be null"); |
| } |
| CollectionUtils.addAll(collection, iterable); |
| } |
| |
| /** |
| * Returns an array containing all elements of this iterable by traversing |
| * its iterator. |
| * |
| * @param arrayClass the class of array to create |
| * @return an array of the iterable contents |
| * @throws ArrayStoreException if arrayClass is invalid |
| */ |
| public E[] toArray(final Class<E> arrayClass) { |
| return IteratorUtils.toArray(iterator(), arrayClass); |
| } |
| |
| /** |
| * Returns a mutable list containing all elements of this iterable |
| * by traversing its iterator. |
| * <p> |
| * The returned list is guaranteed to be mutable. |
| * |
| * @return a list of the iterable contents |
| */ |
| public List<E> toList() { |
| return IterableUtils.toList(iterable); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public String toString() { |
| return IterableUtils.toString(iterable); |
| } |
| |
| } |