/
Sets.java
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/
Sets.java
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/*
* Copyright (C) 2007 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.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.Collections2.FilteredCollection;
import com.google.common.math.IntMath;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.Serializable;
import java.util.AbstractSet;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.NavigableSet;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArraySet;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;
/**
* Static utility methods pertaining to {@link Set} instances. Also see this class's counterparts
* {@link Lists}, {@link Maps} and {@link Queues}.
*
* <p>See the Guava User Guide article on <a href=
* "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#sets"> {@code Sets}</a>.
*
* @author Kevin Bourrillion
* @author Jared Levy
* @author Chris Povirk
* @since 2.0
*/
@GwtCompatible(emulated = true)
public final class Sets {
private Sets() {}
/**
* {@link AbstractSet} substitute without the potentially-quadratic {@code removeAll}
* implementation.
*/
abstract static class ImprovedAbstractSet<E> extends AbstractSet<E> {
@Override
public boolean removeAll(Collection<?> c) {
return removeAllImpl(this, c);
}
@Override
public boolean retainAll(Collection<?> c) {
return super.retainAll(checkNotNull(c)); // GWT compatibility
}
}
/**
* Returns an immutable set instance containing the given enum elements. Internally, the returned
* set will be backed by an {@link EnumSet}.
*
* <p>The iteration order of the returned set follows the enum's iteration order, not the order in
* which the elements are provided to the method.
*
* @param anElement one of the elements the set should contain
* @param otherElements the rest of the elements the set should contain
* @return an immutable set containing those elements, minus duplicates
*/
// http://code.google.com/p/google-web-toolkit/issues/detail?id=3028
@GwtCompatible(serializable = true)
public static <E extends Enum<E>> ImmutableSet<E> immutableEnumSet(
E anElement, E... otherElements) {
return ImmutableEnumSet.asImmutable(EnumSet.of(anElement, otherElements));
}
/**
* Returns an immutable set instance containing the given enum elements. Internally, the returned
* set will be backed by an {@link EnumSet}.
*
* <p>The iteration order of the returned set follows the enum's iteration order, not the order in
* which the elements appear in the given collection.
*
* @param elements the elements, all of the same {@code enum} type, that the set should contain
* @return an immutable set containing those elements, minus duplicates
*/
// http://code.google.com/p/google-web-toolkit/issues/detail?id=3028
@GwtCompatible(serializable = true)
public static <E extends Enum<E>> ImmutableSet<E> immutableEnumSet(Iterable<E> elements) {
if (elements instanceof ImmutableEnumSet) {
return (ImmutableEnumSet<E>) elements;
} else if (elements instanceof Collection) {
Collection<E> collection = (Collection<E>) elements;
if (collection.isEmpty()) {
return ImmutableSet.of();
} else {
return ImmutableEnumSet.asImmutable(EnumSet.copyOf(collection));
}
} else {
Iterator<E> itr = elements.iterator();
if (itr.hasNext()) {
EnumSet<E> enumSet = EnumSet.of(itr.next());
Iterators.addAll(enumSet, itr);
return ImmutableEnumSet.asImmutable(enumSet);
} else {
return ImmutableSet.of();
}
}
}
/**
* Returns a new, <i>mutable</i> {@code EnumSet} instance containing the given elements in their
* natural order. This method behaves identically to {@link EnumSet#copyOf(Collection)}, but also
* accepts non-{@code Collection} iterables and empty iterables.
*/
public static <E extends Enum<E>> EnumSet<E> newEnumSet(
Iterable<E> iterable, Class<E> elementType) {
EnumSet<E> set = EnumSet.noneOf(elementType);
Iterables.addAll(set, iterable);
return set;
}
// HashSet
/**
* Creates a <i>mutable</i>, initially empty {@code HashSet} instance.
*
* <p><b>Note:</b> if mutability is not required, use {@link ImmutableSet#of()} instead. If {@code
* E} is an {@link Enum} type, use {@link EnumSet#noneOf} instead. Otherwise, strongly consider
* using a {@code LinkedHashSet} instead, at the cost of increased memory footprint, to get
* deterministic iteration behavior.
*
* <p><b>Note for Java 7 and later:</b> this method is now unnecessary and should be treated as
* deprecated. Instead, use the {@code HashSet} constructor directly, taking advantage of the new
* <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
*/
public static <E> HashSet<E> newHashSet() {
return new HashSet<E>();
}
/**
* Creates a <i>mutable</i> {@code HashSet} instance initially containing the given elements.
*
* <p><b>Note:</b> if elements are non-null and won't be added or removed after this point, use
* {@link ImmutableSet#of()} or {@link ImmutableSet#copyOf(Object[])} instead. If {@code E} is an
* {@link Enum} type, use {@link EnumSet#of(Enum, Enum[])} instead. Otherwise, strongly consider
* using a {@code LinkedHashSet} instead, at the cost of increased memory footprint, to get
* deterministic iteration behavior.
*
* <p>This method is just a small convenience, either for {@code newHashSet(}{@link Arrays#asList
* asList}{@code (...))}, or for creating an empty set then calling {@link Collections#addAll}.
* This method is not actually very useful and will likely be deprecated in the future.
*/
public static <E> HashSet<E> newHashSet(E... elements) {
HashSet<E> set = newHashSetWithExpectedSize(elements.length);
Collections.addAll(set, elements);
return set;
}
/**
* Creates a <i>mutable</i> {@code HashSet} instance containing the given elements. A very thin
* convenience for creating an empty set then calling {@link Collection#addAll} or {@link
* Iterables#addAll}.
*
* <p><b>Note:</b> if mutability is not required and the elements are non-null, use {@link
* ImmutableSet#copyOf(Iterable)} instead. (Or, change {@code elements} to be a {@link
* FluentIterable} and call {@code elements.toSet()}.)
*
* <p><b>Note:</b> if {@code E} is an {@link Enum} type, use {@link #newEnumSet(Iterable, Class)}
* instead.
*
* <p><b>Note for Java 7 and later:</b> if {@code elements} is a {@link Collection}, you don't
* need this method. Instead, use the {@code HashSet} constructor directly, taking advantage of
* the new <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
*
* <p>Overall, this method is not very useful and will likely be deprecated in the future.
*/
public static <E> HashSet<E> newHashSet(Iterable<? extends E> elements) {
return (elements instanceof Collection)
? new HashSet<E>(Collections2.cast(elements))
: newHashSet(elements.iterator());
}
/**
* Creates a <i>mutable</i> {@code HashSet} instance containing the given elements. A very thin
* convenience for creating an empty set and then calling {@link Iterators#addAll}.
*
* <p><b>Note:</b> if mutability is not required and the elements are non-null, use {@link
* ImmutableSet#copyOf(Iterator)} instead.
*
* <p><b>Note:</b> if {@code E} is an {@link Enum} type, you should create an {@link EnumSet}
* instead.
*
* <p>Overall, this method is not very useful and will likely be deprecated in the future.
*/
public static <E> HashSet<E> newHashSet(Iterator<? extends E> elements) {
HashSet<E> set = newHashSet();
Iterators.addAll(set, elements);
return set;
}
/**
* Returns a new hash set using the smallest initial table size that can hold {@code expectedSize}
* elements without resizing. Note that this is not what {@link HashSet#HashSet(int)} does, but it
* is what most users want and expect it to do.
*
* <p>This behavior can't be broadly guaranteed, but has been tested with OpenJDK 1.7 and 1.8.
*
* @param expectedSize the number of elements you expect to add to the returned set
* @return a new, empty hash set with enough capacity to hold {@code expectedSize} elements
* without resizing
* @throws IllegalArgumentException if {@code expectedSize} is negative
*/
public static <E> HashSet<E> newHashSetWithExpectedSize(int expectedSize) {
return new HashSet<E>(Maps.capacity(expectedSize));
}
/**
* Creates a thread-safe set backed by a hash map. The set is backed by a {@link
* ConcurrentHashMap} instance, and thus carries the same concurrency guarantees.
*
* <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be used as an element. The
* set is serializable.
*
* @return a new, empty thread-safe {@code Set}
* @since 15.0
*/
public static <E> Set<E> newConcurrentHashSet() {
return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
}
/**
* Creates a thread-safe set backed by a hash map and containing the given elements. The set is
* backed by a {@link ConcurrentHashMap} instance, and thus carries the same concurrency
* guarantees.
*
* <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be used as an element. The
* set is serializable.
*
* @param elements the elements that the set should contain
* @return a new thread-safe set containing those elements (minus duplicates)
* @throws NullPointerException if {@code elements} or any of its contents is null
* @since 15.0
*/
public static <E> Set<E> newConcurrentHashSet(Iterable<? extends E> elements) {
Set<E> set = newConcurrentHashSet();
Iterables.addAll(set, elements);
return set;
}
// LinkedHashSet
/**
* Creates a <i>mutable</i>, empty {@code LinkedHashSet} instance.
*
* <p><b>Note:</b> if mutability is not required, use {@link ImmutableSet#of()} instead.
*
* <p><b>Note for Java 7 and later:</b> this method is now unnecessary and should be treated as
* deprecated. Instead, use the {@code LinkedHashSet} constructor directly, taking advantage of
* the new <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
*
* @return a new, empty {@code LinkedHashSet}
*/
public static <E> LinkedHashSet<E> newLinkedHashSet() {
return new LinkedHashSet<E>();
}
/**
* Creates a <i>mutable</i> {@code LinkedHashSet} instance containing the given elements in order.
*
* <p><b>Note:</b> if mutability is not required and the elements are non-null, use {@link
* ImmutableSet#copyOf(Iterable)} instead.
*
* <p><b>Note for Java 7 and later:</b> if {@code elements} is a {@link Collection}, you don't
* need this method. Instead, use the {@code LinkedHashSet} constructor directly, taking advantage
* of the new <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
*
* <p>Overall, this method is not very useful and will likely be deprecated in the future.
*
* @param elements the elements that the set should contain, in order
* @return a new {@code LinkedHashSet} containing those elements (minus duplicates)
*/
public static <E> LinkedHashSet<E> newLinkedHashSet(Iterable<? extends E> elements) {
if (elements instanceof Collection) {
return new LinkedHashSet<E>(Collections2.cast(elements));
}
LinkedHashSet<E> set = newLinkedHashSet();
Iterables.addAll(set, elements);
return set;
}
/**
* Creates a {@code LinkedHashSet} instance, with a high enough "initial capacity" that it
* <i>should</i> hold {@code expectedSize} elements without growth. This behavior cannot be
* broadly guaranteed, but it is observed to be true for OpenJDK 1.7. It also can't be guaranteed
* that the method isn't inadvertently <i>oversizing</i> the returned set.
*
* @param expectedSize the number of elements you expect to add to the returned set
* @return a new, empty {@code LinkedHashSet} with enough capacity to hold {@code expectedSize}
* elements without resizing
* @throws IllegalArgumentException if {@code expectedSize} is negative
* @since 11.0
*/
public static <E> LinkedHashSet<E> newLinkedHashSetWithExpectedSize(int expectedSize) {
return new LinkedHashSet<E>(Maps.capacity(expectedSize));
}
// TreeSet
/**
* Creates a <i>mutable</i>, empty {@code TreeSet} instance sorted by the natural sort ordering of
* its elements.
*
* <p><b>Note:</b> if mutability is not required, use {@link ImmutableSortedSet#of()} instead.
*
* <p><b>Note for Java 7 and later:</b> this method is now unnecessary and should be treated as
* deprecated. Instead, use the {@code TreeSet} constructor directly, taking advantage of the new
* <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
*
* @return a new, empty {@code TreeSet}
*/
public static <E extends Comparable> TreeSet<E> newTreeSet() {
return new TreeSet<E>();
}
/**
* Creates a <i>mutable</i> {@code TreeSet} instance containing the given elements sorted by their
* natural ordering.
*
* <p><b>Note:</b> if mutability is not required, use {@link ImmutableSortedSet#copyOf(Iterable)}
* instead.
*
* <p><b>Note:</b> If {@code elements} is a {@code SortedSet} with an explicit comparator, this
* method has different behavior than {@link TreeSet#TreeSet(SortedSet)}, which returns a {@code
* TreeSet} with that comparator.
*
* <p><b>Note for Java 7 and later:</b> this method is now unnecessary and should be treated as
* deprecated. Instead, use the {@code TreeSet} constructor directly, taking advantage of the new
* <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
*
* <p>This method is just a small convenience for creating an empty set and then calling {@link
* Iterables#addAll}. This method is not very useful and will likely be deprecated in the future.
*
* @param elements the elements that the set should contain
* @return a new {@code TreeSet} containing those elements (minus duplicates)
*/
public static <E extends Comparable> TreeSet<E> newTreeSet(Iterable<? extends E> elements) {
TreeSet<E> set = newTreeSet();
Iterables.addAll(set, elements);
return set;
}
/**
* Creates a <i>mutable</i>, empty {@code TreeSet} instance with the given comparator.
*
* <p><b>Note:</b> if mutability is not required, use {@code
* ImmutableSortedSet.orderedBy(comparator).build()} instead.
*
* <p><b>Note for Java 7 and later:</b> this method is now unnecessary and should be treated as
* deprecated. Instead, use the {@code TreeSet} constructor directly, taking advantage of the new
* <a href="http://goo.gl/iz2Wi">"diamond" syntax</a>. One caveat to this is that the {@code
* TreeSet} constructor uses a null {@code Comparator} to mean "natural ordering," whereas this
* factory rejects null. Clean your code accordingly.
*
* @param comparator the comparator to use to sort the set
* @return a new, empty {@code TreeSet}
* @throws NullPointerException if {@code comparator} is null
*/
public static <E> TreeSet<E> newTreeSet(Comparator<? super E> comparator) {
return new TreeSet<E>(checkNotNull(comparator));
}
/**
* Creates an empty {@code Set} that uses identity to determine equality. It compares object
* references, instead of calling {@code equals}, to determine whether a provided object matches
* an element in the set. For example, {@code contains} returns {@code false} when passed an
* object that equals a set member, but isn't the same instance. This behavior is similar to the
* way {@code IdentityHashMap} handles key lookups.
*
* @since 8.0
*/
public static <E> Set<E> newIdentityHashSet() {
return Collections.newSetFromMap(Maps.<E, Boolean>newIdentityHashMap());
}
/**
* Creates an empty {@code CopyOnWriteArraySet} instance.
*
* <p><b>Note:</b> if you need an immutable empty {@link Set}, use {@link Collections#emptySet}
* instead.
*
* @return a new, empty {@code CopyOnWriteArraySet}
* @since 12.0
*/
@GwtIncompatible // CopyOnWriteArraySet
public static <E> CopyOnWriteArraySet<E> newCopyOnWriteArraySet() {
return new CopyOnWriteArraySet<E>();
}
/**
* Creates a {@code CopyOnWriteArraySet} instance containing the given elements.
*
* @param elements the elements that the set should contain, in order
* @return a new {@code CopyOnWriteArraySet} containing those elements
* @since 12.0
*/
@GwtIncompatible // CopyOnWriteArraySet
public static <E> CopyOnWriteArraySet<E> newCopyOnWriteArraySet(Iterable<? extends E> elements) {
// We copy elements to an ArrayList first, rather than incurring the
// quadratic cost of adding them to the COWAS directly.
Collection<? extends E> elementsCollection =
(elements instanceof Collection)
? Collections2.cast(elements)
: Lists.newArrayList(elements);
return new CopyOnWriteArraySet<E>(elementsCollection);
}
/**
* Creates an {@code EnumSet} consisting of all enum values that are not in the specified
* collection. If the collection is an {@link EnumSet}, this method has the same behavior as
* {@link EnumSet#complementOf}. Otherwise, the specified collection must contain at least one
* element, in order to determine the element type. If the collection could be empty, use {@link
* #complementOf(Collection, Class)} instead of this method.
*
* @param collection the collection whose complement should be stored in the enum set
* @return a new, modifiable {@code EnumSet} containing all values of the enum that aren't present
* in the given collection
* @throws IllegalArgumentException if {@code collection} is not an {@code EnumSet} instance and
* contains no elements
*/
public static <E extends Enum<E>> EnumSet<E> complementOf(Collection<E> collection) {
if (collection instanceof EnumSet) {
return EnumSet.complementOf((EnumSet<E>) collection);
}
checkArgument(
!collection.isEmpty(), "collection is empty; use the other version of this method");
Class<E> type = collection.iterator().next().getDeclaringClass();
return makeComplementByHand(collection, type);
}
/**
* Creates an {@code EnumSet} consisting of all enum values that are not in the specified
* collection. This is equivalent to {@link EnumSet#complementOf}, but can act on any input
* collection, as long as the elements are of enum type.
*
* @param collection the collection whose complement should be stored in the {@code EnumSet}
* @param type the type of the elements in the set
* @return a new, modifiable {@code EnumSet} initially containing all the values of the enum not
* present in the given collection
*/
public static <E extends Enum<E>> EnumSet<E> complementOf(
Collection<E> collection, Class<E> type) {
checkNotNull(collection);
return (collection instanceof EnumSet)
? EnumSet.complementOf((EnumSet<E>) collection)
: makeComplementByHand(collection, type);
}
private static <E extends Enum<E>> EnumSet<E> makeComplementByHand(
Collection<E> collection, Class<E> type) {
EnumSet<E> result = EnumSet.allOf(type);
result.removeAll(collection);
return result;
}
/**
* Returns a set backed by the specified map. The resulting set displays the same ordering,
* concurrency, and performance characteristics as the backing map. In essence, this factory
* method provides a {@link Set} implementation corresponding to any {@link Map} implementation.
* There is no need to use this method on a {@link Map} implementation that already has a
* corresponding {@link Set} implementation (such as {@link java.util.HashMap} or {@link
* java.util.TreeMap}).
*
* <p>Each method invocation on the set returned by this method results in exactly one method
* invocation on the backing map or its {@code keySet} view, with one exception. The {@code
* addAll} method is implemented as a sequence of {@code put} invocations on the backing map.
*
* <p>The specified map must be empty at the time this method is invoked, and should not be
* accessed directly after this method returns. These conditions are ensured if the map is created
* empty, passed directly to this method, and no reference to the map is retained, as illustrated
* in the following code fragment:
*
* <pre>{@code
* Set<Object> identityHashSet = Sets.newSetFromMap(
* new IdentityHashMap<Object, Boolean>());
* }</pre>
*
* <p>The returned set is serializable if the backing map is.
*
* @param map the backing map
* @return the set backed by the map
* @throws IllegalArgumentException if {@code map} is not empty
* @deprecated Use {@link Collections#newSetFromMap} instead.
*/
@Deprecated
public static <E> Set<E> newSetFromMap(Map<E, Boolean> map) {
return Collections.newSetFromMap(map);
}
/**
* An unmodifiable view of a set which may be backed by other sets; this view will change as the
* backing sets do. Contains methods to copy the data into a new set which will then remain
* stable. There is usually no reason to retain a reference of type {@code SetView}; typically,
* you either use it as a plain {@link Set}, or immediately invoke {@link #immutableCopy} or
* {@link #copyInto} and forget the {@code SetView} itself.
*
* @since 2.0
*/
public abstract static class SetView<E> extends AbstractSet<E> {
private SetView() {} // no subclasses but our own
/**
* Returns an immutable copy of the current contents of this set view. Does not support null
* elements.
*
* <p><b>Warning:</b> this may have unexpected results if a backing set of this view uses a
* nonstandard notion of equivalence, for example if it is a {@link TreeSet} using a comparator
* that is inconsistent with {@link Object#equals(Object)}.
*/
public ImmutableSet<E> immutableCopy() {
return ImmutableSet.copyOf(this);
}
/**
* Copies the current contents of this set view into an existing set. This method has equivalent
* behavior to {@code set.addAll(this)}, assuming that all the sets involved are based on the
* same notion of equivalence.
*
* @return a reference to {@code set}, for convenience
*/
// Note: S should logically extend Set<? super E> but can't due to either
// some javac bug or some weirdness in the spec, not sure which.
@CanIgnoreReturnValue
public <S extends Set<E>> S copyInto(S set) {
set.addAll(this);
return set;
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public final boolean add(E e) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public final boolean remove(Object object) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public final boolean addAll(Collection<? extends E> newElements) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public final boolean removeAll(Collection<?> oldElements) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
public final boolean retainAll(Collection<?> elementsToKeep) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final void clear() {
throw new UnsupportedOperationException();
}
/**
* Scope the return type to {@link UnmodifiableIterator} to ensure this is an unmodifiable view.
*
* @since 20.0 (present with return type {@link Iterator} since 2.0)
*/
@Override
public abstract UnmodifiableIterator<E> iterator();
}
/**
* Returns an unmodifiable <b>view</b> of the union of two sets. The returned set contains all
* elements that are contained in either backing set. Iterating over the returned set iterates
* first over all the elements of {@code set1}, then over each element of {@code set2}, in order,
* that is not contained in {@code set1}.
*
* <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
* equivalence relations (as {@link HashSet}, {@link TreeSet}, and the {@link Map#keySet} of an
* {@code IdentityHashMap} all are).
*/
public static <E> SetView<E> union(final Set<? extends E> set1, final Set<? extends E> set2) {
checkNotNull(set1, "set1");
checkNotNull(set2, "set2");
return new SetView<E>() {
@Override
public int size() {
int size = set1.size();
for (E e : set2) {
if (!set1.contains(e)) {
size++;
}
}
return size;
}
@Override
public boolean isEmpty() {
return set1.isEmpty() && set2.isEmpty();
}
@Override
public UnmodifiableIterator<E> iterator() {
return new AbstractIterator<E>() {
final Iterator<? extends E> itr1 = set1.iterator();
final Iterator<? extends E> itr2 = set2.iterator();
@Override
protected E computeNext() {
if (itr1.hasNext()) {
return itr1.next();
}
while (itr2.hasNext()) {
E e = itr2.next();
if (!set1.contains(e)) {
return e;
}
}
return endOfData();
}
};
}
@Override
public boolean contains(Object object) {
return set1.contains(object) || set2.contains(object);
}
@Override
public <S extends Set<E>> S copyInto(S set) {
set.addAll(set1);
set.addAll(set2);
return set;
}
@Override
public ImmutableSet<E> immutableCopy() {
return new ImmutableSet.Builder<E>().addAll(set1).addAll(set2).build();
}
};
}
/**
* Returns an unmodifiable <b>view</b> of the intersection of two sets. The returned set contains
* all elements that are contained by both backing sets. The iteration order of the returned set
* matches that of {@code set1}.
*
* <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
* equivalence relations (as {@code HashSet}, {@code TreeSet}, and the keySet of an {@code
* IdentityHashMap} all are).
*
* <p><b>Note:</b> The returned view performs slightly better when {@code set1} is the smaller of
* the two sets. If you have reason to believe one of your sets will generally be smaller than the
* other, pass it first. Unfortunately, since this method sets the generic type of the returned
* set based on the type of the first set passed, this could in rare cases force you to make a
* cast, for example:
*
* <pre>{@code
* Set<Object> aFewBadObjects = ...
* Set<String> manyBadStrings = ...
*
* // impossible for a non-String to be in the intersection
* SuppressWarnings("unchecked")
* Set<String> badStrings = (Set) Sets.intersection(
* aFewBadObjects, manyBadStrings);
* }</pre>
*
* <p>This is unfortunate, but should come up only very rarely.
*/
public static <E> SetView<E> intersection(final Set<E> set1, final Set<?> set2) {
checkNotNull(set1, "set1");
checkNotNull(set2, "set2");
return new SetView<E>() {
@Override
public UnmodifiableIterator<E> iterator() {
return new AbstractIterator<E>() {
final Iterator<E> itr = set1.iterator();
@Override
protected E computeNext() {
while (itr.hasNext()) {
E e = itr.next();
if (set2.contains(e)) {
return e;
}
}
return endOfData();
}
};
}
@Override
public int size() {
int size = 0;
for (E e : set1) {
if (set2.contains(e)) {
size++;
}
}
return size;
}
@Override
public boolean isEmpty() {
return Collections.disjoint(set2, set1);
}
@Override
public boolean contains(Object object) {
return set1.contains(object) && set2.contains(object);
}
@Override
public boolean containsAll(Collection<?> collection) {
return set1.containsAll(collection) && set2.containsAll(collection);
}
};
}
/**
* Returns an unmodifiable <b>view</b> of the difference of two sets. The returned set contains
* all elements that are contained by {@code set1} and not contained by {@code set2}. {@code set2}
* may also contain elements not present in {@code set1}; these are simply ignored. The iteration
* order of the returned set matches that of {@code set1}.
*
* <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
* equivalence relations (as {@code HashSet}, {@code TreeSet}, and the keySet of an {@code
* IdentityHashMap} all are).
*/
public static <E> SetView<E> difference(final Set<E> set1, final Set<?> set2) {
checkNotNull(set1, "set1");
checkNotNull(set2, "set2");
return new SetView<E>() {
@Override
public UnmodifiableIterator<E> iterator() {
return new AbstractIterator<E>() {
final Iterator<E> itr = set1.iterator();
@Override
protected E computeNext() {
while (itr.hasNext()) {
E e = itr.next();
if (!set2.contains(e)) {
return e;
}
}
return endOfData();
}
};
}
@Override
public int size() {
int size = 0;
for (E e : set1) {
if (!set2.contains(e)) {
size++;
}
}
return size;
}
@Override
public boolean isEmpty() {
return set2.containsAll(set1);
}
@Override
public boolean contains(Object element) {
return set1.contains(element) && !set2.contains(element);
}
};
}
/**
* Returns an unmodifiable <b>view</b> of the symmetric difference of two sets. The returned set
* contains all elements that are contained in either {@code set1} or {@code set2} but not in
* both. The iteration order of the returned set is undefined.
*
* <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
* equivalence relations (as {@code HashSet}, {@code TreeSet}, and the keySet of an {@code
* IdentityHashMap} all are).
*
* @since 3.0
*/
public static <E> SetView<E> symmetricDifference(
final Set<? extends E> set1, final Set<? extends E> set2) {
checkNotNull(set1, "set1");
checkNotNull(set2, "set2");
return new SetView<E>() {
@Override
public UnmodifiableIterator<E> iterator() {
final Iterator<? extends E> itr1 = set1.iterator();
final Iterator<? extends E> itr2 = set2.iterator();
return new AbstractIterator<E>() {
@Override
public E computeNext() {
while (itr1.hasNext()) {
E elem1 = itr1.next();
if (!set2.contains(elem1)) {
return elem1;
}
}
while (itr2.hasNext()) {
E elem2 = itr2.next();
if (!set1.contains(elem2)) {
return elem2;
}
}
return endOfData();
}
};
}
@Override
public int size() {
int size = 0;
for (E e : set1) {
if (!set2.contains(e)) {
size++;
}
}
for (E e : set2) {
if (!set1.contains(e)) {
size++;
}
}
return size;
}
@Override
public boolean isEmpty() {
return set1.equals(set2);
}
@Override
public boolean contains(Object element) {
return set1.contains(element) ^ set2.contains(element);
}
};
}
/**
* Returns the elements of {@code unfiltered} that satisfy a predicate. The returned set is a live
* view of {@code unfiltered}; changes to one affect the other.
*
* <p>The resulting set's iterator does not support {@code remove()}, but all other set methods
* are supported. When given an element that doesn't satisfy the predicate, the set's {@code
* add()} and {@code addAll()} methods throw an {@link IllegalArgumentException}. When methods
* such as {@code removeAll()} and {@code clear()} are called on the filtered set, only elements
* that satisfy the filter will be removed from the underlying set.
*
* <p>The returned set isn't threadsafe or serializable, even if {@code unfiltered} is.
*
* <p>Many of the filtered set's methods, such as {@code size()}, iterate across every element in
* the underlying set and determine which elements satisfy the filter. When a live view is
* <i>not</i> needed, it may be faster to copy {@code Iterables.filter(unfiltered, predicate)} and
* use the copy.
*
* <p><b>Warning:</b> {@code predicate} must be <i>consistent with equals</i>, as documented at
* {@link Predicate#apply}. Do not provide a predicate such as {@code
* Predicates.instanceOf(ArrayList.class)}, which is inconsistent with equals. (See {@link
* Iterables#filter(Iterable, Class)} for related functionality.)
*
* <p><b>Java 8 users:</b> many use cases for this method are better addressed by {@link
* java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
* you to migrate to streams.
*/
// TODO(kevinb): how to omit that last sentence when building GWT javadoc?
public static <E> Set<E> filter(Set<E> unfiltered, Predicate<? super E> predicate) {
if (unfiltered instanceof SortedSet) {
return filter((SortedSet<E>) unfiltered, predicate);
}
if (unfiltered instanceof FilteredSet) {
// Support clear(), removeAll(), and retainAll() when filtering a filtered
// collection.
FilteredSet<E> filtered = (FilteredSet<E>) unfiltered;
Predicate<E> combinedPredicate = Predicates.<E>and(filtered.predicate, predicate);
return new FilteredSet<E>((Set<E>) filtered.unfiltered, combinedPredicate);
}
return new FilteredSet<E>(checkNotNull(unfiltered), checkNotNull(predicate));
}
/**
* Returns the elements of a {@code SortedSet}, {@code unfiltered}, that satisfy a predicate. The
* returned set is a live view of {@code unfiltered}; changes to one affect the other.
*
* <p>The resulting set's iterator does not support {@code remove()}, but all other set methods
* are supported. When given an element that doesn't satisfy the predicate, the set's {@code
* add()} and {@code addAll()} methods throw an {@link IllegalArgumentException}. When methods
* such as {@code removeAll()} and {@code clear()} are called on the filtered set, only elements
* that satisfy the filter will be removed from the underlying set.
*
* <p>The returned set isn't threadsafe or serializable, even if {@code unfiltered} is.
*
* <p>Many of the filtered set's methods, such as {@code size()}, iterate across every element in
* the underlying set and determine which elements satisfy the filter. When a live view is
* <i>not</i> needed, it may be faster to copy {@code Iterables.filter(unfiltered, predicate)} and
* use the copy.
*
* <p><b>Warning:</b> {@code predicate} must be <i>consistent with equals</i>, as documented at
* {@link Predicate#apply}. Do not provide a predicate such as {@code
* Predicates.instanceOf(ArrayList.class)}, which is inconsistent with equals. (See {@link
* Iterables#filter(Iterable, Class)} for related functionality.)
*
* @since 11.0
*/
public static <E> SortedSet<E> filter(SortedSet<E> unfiltered, Predicate<? super E> predicate) {
if (unfiltered instanceof FilteredSet) {
// Support clear(), removeAll(), and retainAll() when filtering a filtered
// collection.
FilteredSet<E> filtered = (FilteredSet<E>) unfiltered;
Predicate<E> combinedPredicate = Predicates.<E>and(filtered.predicate, predicate);
return new FilteredSortedSet<E>((SortedSet<E>) filtered.unfiltered, combinedPredicate);
}