| /* |
| * Copyright (C) 2008 The Guava Authors |
| * |
| * Licensed 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 com.google.common.collect; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| import com.google.common.annotations.Beta; |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.common.base.Function; |
| import com.google.common.base.Joiner; |
| import com.google.common.base.Optional; |
| import com.google.common.base.Predicate; |
| |
| import java.util.Arrays; |
| import java.util.Collection; |
| import java.util.Comparator; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.SortedSet; |
| |
| import javax.annotation.CheckReturnValue; |
| import javax.annotation.Nullable; |
| |
| /** |
| * {@code FluentIterable} provides a rich interface for manipulating {@code Iterable} instances in a |
| * chained fashion. A {@code FluentIterable} can be created from an {@code Iterable}, or from a set |
| * of elements. The following types of methods are provided on {@code FluentIterable}: |
| * <ul> |
| * <li>chained methods which return a new {@code FluentIterable} based in some way on the contents |
| * of the current one (for example {@link #transform}) |
| * <li>conversion methods which copy the {@code FluentIterable}'s contents into a new collection or |
| * array (for example {@link #toList}) |
| * <li>element extraction methods which facilitate the retrieval of certain elements (for example |
| * {@link #last}) |
| * <li>query methods which answer questions about the {@code FluentIterable}'s contents (for example |
| * {@link #anyMatch}) |
| * </ul> |
| * |
| * <p>Here is an example that merges the lists returned by two separate database calls, transforms |
| * it by invoking {@code toString()} on each element, and returns the first 10 elements as an |
| * {@code ImmutableList}: <pre> {@code |
| * |
| * FluentIterable |
| * .from(database.getClientList()) |
| * .filter(activeInLastMonth()) |
| * .transform(Functions.toStringFunction()) |
| * .limit(10) |
| * .toList();}</pre> |
| * |
| * <p>Anything which can be done using {@code FluentIterable} could be done in a different fashion |
| * (often with {@link Iterables}), however the use of {@code FluentIterable} makes many sets of |
| * operations significantly more concise. |
| * |
| * @author Marcin Mikosik |
| * @since 12.0 |
| */ |
| @GwtCompatible(emulated = true) |
| public abstract class FluentIterable<E> implements Iterable<E> { |
| // We store 'iterable' and use it instead of 'this' to allow Iterables to perform instanceof |
| // checks on the _original_ iterable when FluentIterable.from is used. |
| private final Iterable<E> iterable; |
| |
| /** Constructor for use by subclasses. */ |
| protected FluentIterable() { |
| this.iterable = this; |
| } |
| |
| FluentIterable(Iterable<E> iterable) { |
| this.iterable = checkNotNull(iterable); |
| } |
| |
| /** |
| * Returns a fluent iterable that wraps {@code iterable}, or {@code iterable} itself if it |
| * is already a {@code FluentIterable}. |
| */ |
| public static <E> FluentIterable<E> from(final Iterable<E> iterable) { |
| return (iterable instanceof FluentIterable) ? (FluentIterable<E>) iterable |
| : new FluentIterable<E>(iterable) { |
| @Override |
| public Iterator<E> iterator() { |
| return iterable.iterator(); |
| } |
| }; |
| } |
| |
| /** |
| * Construct a fluent iterable from another fluent iterable. This is obviously never necessary, |
| * but is intended to help call out cases where one migration from {@code Iterable} to |
| * {@code FluentIterable} has obviated the need to explicitly convert to a {@code FluentIterable}. |
| * |
| * @deprecated instances of {@code FluentIterable} don't need to be converted to |
| * {@code FluentIterable} |
| */ |
| @Deprecated |
| public static <E> FluentIterable<E> from(FluentIterable<E> iterable) { |
| return checkNotNull(iterable); |
| } |
| |
| /** |
| * Returns a fluent iterable containing {@code elements} in the specified order. |
| * |
| * @since 18.0 |
| */ |
| @Beta |
| public static <E> FluentIterable<E> of(E[] elements) { |
| return from(Lists.newArrayList(elements)); |
| } |
| |
| /** |
| * Returns a string representation of this fluent iterable, with the format |
| * {@code [e1, e2, ..., en]}. |
| */ |
| @Override |
| public String toString() { |
| return Iterables.toString(iterable); |
| } |
| |
| /** |
| * Returns the number of elements in this fluent iterable. |
| */ |
| public final int size() { |
| return Iterables.size(iterable); |
| } |
| |
| /** |
| * Returns {@code true} if this fluent iterable contains any object for which |
| * {@code equals(element)} is true. |
| */ |
| public final boolean contains(@Nullable Object element) { |
| return Iterables.contains(iterable, element); |
| } |
| |
| /** |
| * Returns a fluent iterable whose {@code Iterator} cycles indefinitely over the elements of |
| * this fluent iterable. |
| * |
| * <p>That iterator supports {@code remove()} if {@code iterable.iterator()} does. After |
| * {@code remove()} is called, subsequent cycles omit the removed element, which is no longer in |
| * this fluent iterable. The iterator's {@code hasNext()} method returns {@code true} until |
| * this fluent iterable is empty. |
| * |
| * <p><b>Warning:</b> Typical uses of the resulting iterator may produce an infinite loop. You |
| * should use an explicit {@code break} or be certain that you will eventually remove all the |
| * elements. |
| */ |
| @CheckReturnValue |
| public final FluentIterable<E> cycle() { |
| return from(Iterables.cycle(iterable)); |
| } |
| |
| /** |
| * Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable, |
| * followed by those of {@code other}. The iterators are not polled until necessary. |
| * |
| * <p>The returned iterable's {@code Iterator} supports {@code remove()} when the corresponding |
| * {@code Iterator} supports it. |
| * |
| * @since 18.0 |
| */ |
| @Beta |
| @CheckReturnValue |
| public final FluentIterable<E> append(Iterable<? extends E> other) { |
| return from(Iterables.concat(iterable, other)); |
| } |
| |
| /** |
| * Returns a fluent iterable whose iterators traverse first the elements of this fluent iterable, |
| * followed by {@code elements}. |
| * |
| * @since 18.0 |
| */ |
| @Beta |
| @CheckReturnValue |
| public final FluentIterable<E> append(E... elements) { |
| return from(Iterables.concat(iterable, Arrays.asList(elements))); |
| } |
| |
| /** |
| * Returns the elements from this fluent iterable that satisfy a predicate. The |
| * resulting fluent iterable's iterator does not support {@code remove()}. |
| */ |
| @CheckReturnValue |
| public final FluentIterable<E> filter(Predicate<? super E> predicate) { |
| return from(Iterables.filter(iterable, predicate)); |
| } |
| |
| /** |
| * Returns {@code true} if any element in this fluent iterable satisfies the predicate. |
| */ |
| public final boolean anyMatch(Predicate<? super E> predicate) { |
| return Iterables.any(iterable, predicate); |
| } |
| |
| /** |
| * Returns {@code true} if every element in this fluent iterable satisfies the predicate. |
| * If this fluent iterable is empty, {@code true} is returned. |
| */ |
| public final boolean allMatch(Predicate<? super E> predicate) { |
| return Iterables.all(iterable, predicate); |
| } |
| |
| /** |
| * Returns an {@link Optional} containing the first element in this fluent iterable that |
| * satisfies the given predicate, if such an element exists. |
| * |
| * <p><b>Warning:</b> avoid using a {@code predicate} that matches {@code null}. If {@code null} |
| * is matched in this fluent iterable, a {@link NullPointerException} will be thrown. |
| */ |
| public final Optional<E> firstMatch(Predicate<? super E> predicate) { |
| return Iterables.tryFind(iterable, predicate); |
| } |
| |
| /** |
| * Returns a fluent iterable that applies {@code function} to each element of this |
| * fluent iterable. |
| * |
| * <p>The returned fluent iterable's iterator supports {@code remove()} if this iterable's |
| * iterator does. After a successful {@code remove()} call, this fluent iterable no longer |
| * contains the corresponding element. |
| */ |
| public final <T> FluentIterable<T> transform(Function<? super E, T> function) { |
| return from(Iterables.transform(iterable, function)); |
| } |
| |
| /** |
| * Applies {@code function} to each element of this fluent iterable and returns |
| * a fluent iterable with the concatenated combination of results. {@code function} |
| * returns an Iterable of results. |
| * |
| * <p>The returned fluent iterable's iterator supports {@code remove()} if this |
| * function-returned iterables' iterator does. After a successful {@code remove()} call, |
| * the returned fluent iterable no longer contains the corresponding element. |
| * |
| * @since 13.0 (required {@code Function<E, Iterable<T>>} until 14.0) |
| */ |
| public <T> FluentIterable<T> transformAndConcat( |
| Function<? super E, ? extends Iterable<? extends T>> function) { |
| return from(Iterables.concat(transform(function))); |
| } |
| |
| /** |
| * Returns an {@link Optional} containing the first element in this fluent iterable. |
| * If the iterable is empty, {@code Optional.absent()} is returned. |
| * |
| * @throws NullPointerException if the first element is null; if this is a possibility, use |
| * {@code iterator().next()} or {@link Iterables#getFirst} instead. |
| */ |
| public final Optional<E> first() { |
| Iterator<E> iterator = iterable.iterator(); |
| return iterator.hasNext() |
| ? Optional.of(iterator.next()) |
| : Optional.<E>absent(); |
| } |
| |
| /** |
| * Returns an {@link Optional} containing the last element in this fluent iterable. |
| * If the iterable is empty, {@code Optional.absent()} is returned. |
| * |
| * @throws NullPointerException if the last element is null; if this is a possibility, use |
| * {@link Iterables#getLast} instead. |
| */ |
| public final Optional<E> last() { |
| // Iterables#getLast was inlined here so we don't have to throw/catch a NSEE |
| |
| // TODO(kevinb): Support a concurrently modified collection? |
| if (iterable instanceof List) { |
| List<E> list = (List<E>) iterable; |
| if (list.isEmpty()) { |
| return Optional.absent(); |
| } |
| return Optional.of(list.get(list.size() - 1)); |
| } |
| Iterator<E> iterator = iterable.iterator(); |
| if (!iterator.hasNext()) { |
| return Optional.absent(); |
| } |
| |
| /* |
| * TODO(kevinb): consider whether this "optimization" is worthwhile. Users |
| * with SortedSets tend to know they are SortedSets and probably would not |
| * call this method. |
| */ |
| if (iterable instanceof SortedSet) { |
| SortedSet<E> sortedSet = (SortedSet<E>) iterable; |
| return Optional.of(sortedSet.last()); |
| } |
| |
| while (true) { |
| E current = iterator.next(); |
| if (!iterator.hasNext()) { |
| return Optional.of(current); |
| } |
| } |
| } |
| |
| /** |
| * Returns a view of this fluent iterable that skips its first {@code numberToSkip} |
| * elements. If this fluent iterable contains fewer than {@code numberToSkip} elements, |
| * the returned fluent iterable skips all of its elements. |
| * |
| * <p>Modifications to this fluent iterable before a call to {@code iterator()} are |
| * reflected in the returned fluent iterable. That is, the its iterator skips the first |
| * {@code numberToSkip} elements that exist when the iterator is created, not when {@code skip()} |
| * is called. |
| * |
| * <p>The returned fluent iterable's iterator supports {@code remove()} if the |
| * {@code Iterator} of this fluent iterable supports it. Note that it is <i>not</i> |
| * possible to delete the last skipped element by immediately calling {@code remove()} on the |
| * returned fluent iterable's iterator, as the {@code Iterator} contract states that a call |
| * to {@code * remove()} before a call to {@code next()} will throw an |
| * {@link IllegalStateException}. |
| */ |
| @CheckReturnValue |
| public final FluentIterable<E> skip(int numberToSkip) { |
| return from(Iterables.skip(iterable, numberToSkip)); |
| } |
| |
| /** |
| * Creates a fluent iterable with the first {@code size} elements of this |
| * fluent iterable. If this fluent iterable does not contain that many elements, |
| * the returned fluent iterable will have the same behavior as this fluent iterable. |
| * The returned fluent iterable's iterator supports {@code remove()} if this |
| * fluent iterable's iterator does. |
| * |
| * @param size the maximum number of elements in the returned fluent iterable |
| * @throws IllegalArgumentException if {@code size} is negative |
| */ |
| @CheckReturnValue |
| public final FluentIterable<E> limit(int size) { |
| return from(Iterables.limit(iterable, size)); |
| } |
| |
| /** |
| * Determines whether this fluent iterable is empty. |
| */ |
| public final boolean isEmpty() { |
| return !iterable.iterator().hasNext(); |
| } |
| |
| /** |
| * Returns an {@code ImmutableList} containing all of the elements from this fluent iterable in |
| * proper sequence. |
| * |
| * @since 14.0 (since 12.0 as {@code toImmutableList()}). |
| */ |
| public final ImmutableList<E> toList() { |
| return ImmutableList.copyOf(iterable); |
| } |
| |
| /** |
| * Returns an {@code ImmutableList} containing all of the elements from this {@code |
| * FluentIterable} in the order specified by {@code comparator}. To produce an {@code |
| * ImmutableList} sorted by its natural ordering, use {@code toSortedList(Ordering.natural())}. |
| * |
| * @param comparator the function by which to sort list elements |
| * @throws NullPointerException if any element is null |
| * @since 14.0 (since 13.0 as {@code toSortedImmutableList()}). |
| */ |
| public final ImmutableList<E> toSortedList(Comparator<? super E> comparator) { |
| return Ordering.from(comparator).immutableSortedCopy(iterable); |
| } |
| |
| /** |
| * Returns an {@code ImmutableSet} containing all of the elements from this fluent iterable with |
| * duplicates removed. |
| * |
| * @since 14.0 (since 12.0 as {@code toImmutableSet()}). |
| */ |
| public final ImmutableSet<E> toSet() { |
| return ImmutableSet.copyOf(iterable); |
| } |
| |
| /** |
| * Returns an {@code ImmutableSortedSet} containing all of the elements from this {@code |
| * FluentIterable} in the order specified by {@code comparator}, with duplicates (determined by |
| * {@code comparator.compare(x, y) == 0}) removed. To produce an {@code ImmutableSortedSet} sorted |
| * by its natural ordering, use {@code toSortedSet(Ordering.natural())}. |
| * |
| * @param comparator the function by which to sort set elements |
| * @throws NullPointerException if any element is null |
| * @since 14.0 (since 12.0 as {@code toImmutableSortedSet()}). |
| */ |
| public final ImmutableSortedSet<E> toSortedSet(Comparator<? super E> comparator) { |
| return ImmutableSortedSet.copyOf(comparator, iterable); |
| } |
| |
| /** |
| * Returns an immutable map for which the elements of this {@code FluentIterable} are the keys in |
| * the same order, mapped to values by the given function. If this iterable contains duplicate |
| * elements, the returned map will contain each distinct element once in the order it first |
| * appears. |
| * |
| * @throws NullPointerException if any element of this iterable is {@code null}, or if {@code |
| * valueFunction} produces {@code null} for any key |
| * @since 14.0 |
| */ |
| public final <V> ImmutableMap<E, V> toMap(Function<? super E, V> valueFunction) { |
| return Maps.toMap(iterable, valueFunction); |
| } |
| |
| /** |
| * Creates an index {@code ImmutableListMultimap} that contains the results of applying a |
| * specified function to each item in this {@code FluentIterable} of values. Each element of this |
| * iterable will be stored as a value in the resulting multimap, yielding a multimap with the same |
| * size as this iterable. The key used to store that value in the multimap will be the result of |
| * calling the function on that value. The resulting multimap is created as an immutable snapshot. |
| * In the returned multimap, keys appear in the order they are first encountered, and the values |
| * corresponding to each key appear in the same order as they are encountered. |
| * |
| * @param keyFunction the function used to produce the key for each value |
| * @throws NullPointerException if any of the following cases is true: |
| * <ul> |
| * <li>{@code keyFunction} is null |
| * <li>An element in this fluent iterable is null |
| * <li>{@code keyFunction} returns {@code null} for any element of this iterable |
| * </ul> |
| * @since 14.0 |
| */ |
| public final <K> ImmutableListMultimap<K, E> index(Function<? super E, K> keyFunction) { |
| return Multimaps.index(iterable, keyFunction); |
| } |
| |
| /** |
| * Returns an immutable map for which the {@link java.util.Map#values} are the elements of this |
| * {@code FluentIterable} in the given order, and each key is the product of invoking a supplied |
| * function on its corresponding value. |
| * |
| * @param keyFunction the function used to produce the key for each value |
| * @throws IllegalArgumentException if {@code keyFunction} produces the same key for more than one |
| * value in this fluent iterable |
| * @throws NullPointerException if any element of this fluent iterable is null, or if |
| * {@code keyFunction} produces {@code null} for any value |
| * @since 14.0 |
| */ |
| public final <K> ImmutableMap<K, E> uniqueIndex(Function<? super E, K> keyFunction) { |
| return Maps.uniqueIndex(iterable, keyFunction); |
| } |
| |
| /** |
| * Copies all the elements from this fluent iterable to {@code collection}. This is equivalent to |
| * calling {@code Iterables.addAll(collection, this)}. |
| * |
| * @param collection the collection to copy elements to |
| * @return {@code collection}, for convenience |
| * @since 14.0 |
| */ |
| public final <C extends Collection<? super E>> C copyInto(C collection) { |
| checkNotNull(collection); |
| if (iterable instanceof Collection) { |
| collection.addAll(Collections2.cast(iterable)); |
| } else { |
| for (E item : iterable) { |
| collection.add(item); |
| } |
| } |
| return collection; |
| } |
| |
| /** |
| * Returns a {@link String} containing all of the elements of this fluent iterable joined with |
| * {@code joiner}. |
| * |
| * @since 18.0 |
| */ |
| @Beta |
| public final String join(Joiner joiner) { |
| return joiner.join(this); |
| } |
| |
| /** |
| * Returns the element at the specified position in this fluent iterable. |
| * |
| * @param position position of the element to return |
| * @return the element at the specified position in this fluent iterable |
| * @throws IndexOutOfBoundsException if {@code position} is negative or greater than or equal to |
| * the size of this fluent iterable |
| */ |
| public final E get(int position) { |
| return Iterables.get(iterable, position); |
| } |
| |
| /** |
| * Function that transforms {@code Iterable<E>} into a fluent iterable. |
| */ |
| private static class FromIterableFunction<E> |
| implements Function<Iterable<E>, FluentIterable<E>> { |
| @Override |
| public FluentIterable<E> apply(Iterable<E> fromObject) { |
| return FluentIterable.from(fromObject); |
| } |
| } |
| } |