eaglercraft-1.8/sources/main/java/com/google/common/collect/FluentIterable.java

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2022-12-25 01:12:28 -08:00
/*
* 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 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;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Function;
import com.google.common.base.Optional;
import com.google.common.base.Predicate;
/**
* {@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 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 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 the elements from this fluent iterable that are instances of class
* {@code type}.
*
* @param type the type of elements desired
*/
@GwtIncompatible("Class.isInstance")
@CheckReturnValue
public final <T> FluentIterable<T> filter(Class<T> type) {
return from(Iterables.filter(iterable, type));
}
/**
* 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()}).
*/
@Beta
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);
}
/**
* Returns an array containing all of the elements from this fluent iterable in
* iteration order.
*
* @param type the type of the elements
* @return a newly-allocated array into which all the elements of this fluent
* iterable have been copied
*/
@GwtIncompatible("Array.newArray(Class, int)")
public final E[] toArray(Class<E> type) {
return Iterables.toArray(iterable, type);
}
/**
* 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 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);
}
}
}