com.google.common.collect.ImmutableMultiset Maven / Gradle / Ivy
/*
* 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 static java.util.Objects.requireNonNull;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.concurrent.LazyInit;
import com.google.j2objc.annotations.WeakOuter;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.function.Function;
import java.util.function.ToIntFunction;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* A {@link Multiset} whose contents will never change, with many other important properties
* detailed at {@link ImmutableCollection}.
*
* Grouped iteration. In all current implementations, duplicate elements always appear
* consecutively when iterating. Elements iterate in order by the first appearance of that
* element when the multiset was created.
*
*
See the Guava User Guide article on immutable collections.
*
* @author Jared Levy
* @author Louis Wasserman
* @since 2.0
*/
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
public abstract class ImmutableMultiset extends ImmutableMultisetGwtSerializationDependencies
implements Multiset {
/**
* Returns a {@code Collector} that accumulates the input elements into a new {@code
* ImmutableMultiset}. Elements iterate in order by the first appearance of that element in
* encounter order.
*
* @since 21.0
*/
public static Collector> toImmutableMultiset() {
return CollectCollectors.toImmutableMultiset(Function.identity(), e -> 1);
}
/**
* Returns a {@code Collector} that accumulates elements into an {@code ImmutableMultiset} whose
* elements are the result of applying {@code elementFunction} to the inputs, with counts equal to
* the result of applying {@code countFunction} to the inputs.
*
* If the mapped elements contain duplicates (according to {@link Object#equals}), the first
* occurrence in encounter order appears in the resulting multiset, with count equal to the sum of
* the outputs of {@code countFunction.applyAsInt(t)} for each {@code t} mapped to that element.
*
* @since 22.0
*/
public static
Collector> toImmutableMultiset(
Function elementFunction,
ToIntFunction countFunction) {
return CollectCollectors.toImmutableMultiset(elementFunction, countFunction);
}
/**
* Returns the empty immutable multiset.
*
* Performance note: the instance returned is a singleton.
*/
@SuppressWarnings("unchecked") // all supported methods are covariant
public static ImmutableMultiset of() {
return (ImmutableMultiset) RegularImmutableMultiset.EMPTY;
}
/**
* Returns an immutable multiset containing a single element.
*
* @throws NullPointerException if {@code element} is null
* @since 6.0 (source-compatible since 2.0)
*/
public static ImmutableMultiset of(E element) {
return copyFromElements(element);
}
/**
* Returns an immutable multiset containing the given elements, in order.
*
* @throws NullPointerException if any element is null
* @since 6.0 (source-compatible since 2.0)
*/
public static ImmutableMultiset of(E e1, E e2) {
return copyFromElements(e1, e2);
}
/**
* Returns an immutable multiset containing the given elements, in the "grouped iteration order"
* described in the class documentation.
*
* @throws NullPointerException if any element is null
* @since 6.0 (source-compatible since 2.0)
*/
public static ImmutableMultiset of(E e1, E e2, E e3) {
return copyFromElements(e1, e2, e3);
}
/**
* Returns an immutable multiset containing the given elements, in the "grouped iteration order"
* described in the class documentation.
*
* @throws NullPointerException if any element is null
* @since 6.0 (source-compatible since 2.0)
*/
public static ImmutableMultiset of(E e1, E e2, E e3, E e4) {
return copyFromElements(e1, e2, e3, e4);
}
/**
* Returns an immutable multiset containing the given elements, in the "grouped iteration order"
* described in the class documentation.
*
* @throws NullPointerException if any element is null
* @since 6.0 (source-compatible since 2.0)
*/
public static ImmutableMultiset of(E e1, E e2, E e3, E e4, E e5) {
return copyFromElements(e1, e2, e3, e4, e5);
}
/**
* Returns an immutable multiset containing the given elements, in the "grouped iteration order"
* described in the class documentation.
*
* @throws NullPointerException if any element is null
* @since 6.0 (source-compatible since 2.0)
*/
public static ImmutableMultiset of(E e1, E e2, E e3, E e4, E e5, E e6, E... others) {
return new Builder().add(e1).add(e2).add(e3).add(e4).add(e5).add(e6).add(others).build();
}
/**
* Returns an immutable multiset containing the given elements, in the "grouped iteration order"
* described in the class documentation.
*
* @throws NullPointerException if any of {@code elements} is null
* @since 6.0
*/
public static ImmutableMultiset copyOf(E[] elements) {
return copyFromElements(elements);
}
/**
* Returns an immutable multiset containing the given elements, in the "grouped iteration order"
* described in the class documentation.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableMultiset copyOf(Iterable elements) {
if (elements instanceof ImmutableMultiset) {
@SuppressWarnings("unchecked") // all supported methods are covariant
ImmutableMultiset result = (ImmutableMultiset) elements;
if (!result.isPartialView()) {
return result;
}
}
Multiset multiset =
(elements instanceof Multiset)
? Multisets.cast(elements)
: LinkedHashMultiset.create(elements);
return copyFromEntries(multiset.entrySet());
}
/**
* Returns an immutable multiset containing the given elements, in the "grouped iteration order"
* described in the class documentation.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableMultiset copyOf(Iterator elements) {
Multiset multiset = LinkedHashMultiset.create();
Iterators.addAll(multiset, elements);
return copyFromEntries(multiset.entrySet());
}
private static ImmutableMultiset copyFromElements(E... elements) {
Multiset multiset = LinkedHashMultiset.create();
Collections.addAll(multiset, elements);
return copyFromEntries(multiset.entrySet());
}
static ImmutableMultiset copyFromEntries(
Collection> entries) {
if (entries.isEmpty()) {
return of();
} else {
return RegularImmutableMultiset.create(entries);
}
}
ImmutableMultiset() {}
@Override
public UnmodifiableIterator iterator() {
final Iterator> entryIterator = entrySet().iterator();
return new UnmodifiableIterator() {
int remaining;
@CheckForNull E element;
@Override
public boolean hasNext() {
return (remaining > 0) || entryIterator.hasNext();
}
@Override
public E next() {
if (remaining <= 0) {
Entry entry = entryIterator.next();
element = entry.getElement();
remaining = entry.getCount();
}
remaining--;
/*
* requireNonNull is safe because `remaining` starts at 0, forcing us to initialize
* `element` above. After that, we never clear it.
*/
return requireNonNull(element);
}
};
}
@LazyInit @CheckForNull private transient ImmutableList asList;
@Override
public ImmutableList asList() {
ImmutableList result = asList;
return (result == null) ? asList = super.asList() : result;
}
@Override
public boolean contains(@CheckForNull Object object) {
return count(object) > 0;
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
@DoNotCall("Always throws UnsupportedOperationException")
public final int add(E element, int occurrences) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
@DoNotCall("Always throws UnsupportedOperationException")
public final int remove(@CheckForNull Object element, int occurrences) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
@DoNotCall("Always throws UnsupportedOperationException")
public final int setCount(E element, int count) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@CanIgnoreReturnValue
@Deprecated
@Override
@DoNotCall("Always throws UnsupportedOperationException")
public final boolean setCount(E element, int oldCount, int newCount) {
throw new UnsupportedOperationException();
}
@GwtIncompatible // not present in emulated superclass
@Override
int copyIntoArray(@Nullable Object[] dst, int offset) {
for (Multiset.Entry entry : entrySet()) {
Arrays.fill(dst, offset, offset + entry.getCount(), entry.getElement());
offset += entry.getCount();
}
return offset;
}
@Override
public boolean equals(@CheckForNull Object object) {
return Multisets.equalsImpl(this, object);
}
@Override
public int hashCode() {
return Sets.hashCodeImpl(entrySet());
}
@Override
public String toString() {
return entrySet().toString();
}
/** @since 21.0 (present with return type {@code Set} since 2.0) */
@Override
public abstract ImmutableSet elementSet();
@LazyInit @CheckForNull private transient ImmutableSet> entrySet;
@Override
public ImmutableSet> entrySet() {
ImmutableSet> es = entrySet;
return (es == null) ? (entrySet = createEntrySet()) : es;
}
private ImmutableSet> createEntrySet() {
return isEmpty() ? ImmutableSet.>of() : new EntrySet();
}
abstract Entry getEntry(int index);
@WeakOuter
private final class EntrySet extends IndexedImmutableSet> {
@Override
boolean isPartialView() {
return ImmutableMultiset.this.isPartialView();
}
@Override
Entry get(int index) {
return getEntry(index);
}
@Override
public int size() {
return elementSet().size();
}
@Override
public boolean contains(@CheckForNull Object o) {
if (o instanceof Entry) {
Entry entry = (Entry) o;
if (entry.getCount() <= 0) {
return false;
}
int count = count(entry.getElement());
return count == entry.getCount();
}
return false;
}
@Override
public int hashCode() {
return ImmutableMultiset.this.hashCode();
}
@GwtIncompatible
@J2ktIncompatible
@Override
Object writeReplace() {
return new EntrySetSerializedForm(ImmutableMultiset.this);
}
@GwtIncompatible
@J2ktIncompatible
private void readObject(ObjectInputStream stream) throws InvalidObjectException {
throw new InvalidObjectException("Use EntrySetSerializedForm");
}
@J2ktIncompatible private static final long serialVersionUID = 0;
}
@GwtIncompatible
@J2ktIncompatible
static class EntrySetSerializedForm implements Serializable {
final ImmutableMultiset multiset;
EntrySetSerializedForm(ImmutableMultiset multiset) {
this.multiset = multiset;
}
Object readResolve() {
return multiset.entrySet();
}
}
@GwtIncompatible
@J2ktIncompatible
@Override
Object writeReplace() {
return new SerializedForm(this);
}
@GwtIncompatible
@J2ktIncompatible
private void readObject(ObjectInputStream stream) throws InvalidObjectException {
throw new InvalidObjectException("Use SerializedForm");
}
/**
* Returns a new builder. The generated builder is equivalent to the builder created by the {@link
* Builder} constructor.
*/
public static Builder builder() {
return new Builder();
}
/**
* A builder for creating immutable multiset instances, especially {@code public static final}
* multisets ("constant multisets"). Example:
*
* {@code
* public static final ImmutableMultiset BEANS =
* new ImmutableMultiset.Builder()
* .addCopies(Bean.COCOA, 4)
* .addCopies(Bean.GARDEN, 6)
* .addCopies(Bean.RED, 8)
* .addCopies(Bean.BLACK_EYED, 10)
* .build();
* }
*
* Builder instances can be reused; it is safe to call {@link #build} multiple times to build
* multiple multisets in series.
*
* @since 2.0
*/
public static class Builder extends ImmutableCollection.Builder {
final Multiset contents;
/**
* Creates a new builder. The returned builder is equivalent to the builder generated by {@link
* ImmutableMultiset#builder}.
*/
public Builder() {
this(LinkedHashMultiset.create());
}
Builder(Multiset contents) {
this.contents = contents;
}
/**
* Adds {@code element} to the {@code ImmutableMultiset}.
*
* @param element the element to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code element} is null
*/
@CanIgnoreReturnValue
@Override
public Builder add(E element) {
contents.add(checkNotNull(element));
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableMultiset}.
*
* @param elements the elements to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null element
*/
@CanIgnoreReturnValue
@Override
public Builder add(E... elements) {
super.add(elements);
return this;
}
/**
* Adds a number of occurrences of an element to this {@code ImmutableMultiset}.
*
* @param element the element to add
* @param occurrences the number of occurrences of the element to add. May be zero, in which
* case no change will be made.
* @return this {@code Builder} object
* @throws NullPointerException if {@code element} is null
* @throws IllegalArgumentException if {@code occurrences} is negative, or if this operation
* would result in more than {@link Integer#MAX_VALUE} occurrences of the element
*/
@CanIgnoreReturnValue
public Builder addCopies(E element, int occurrences) {
contents.add(checkNotNull(element), occurrences);
return this;
}
/**
* Adds or removes the necessary occurrences of an element such that the element attains the
* desired count.
*
* @param element the element to add or remove occurrences of
* @param count the desired count of the element in this multiset
* @return this {@code Builder} object
* @throws NullPointerException if {@code element} is null
* @throws IllegalArgumentException if {@code count} is negative
*/
@CanIgnoreReturnValue
public Builder setCount(E element, int count) {
contents.setCount(checkNotNull(element), count);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableMultiset}.
*
* @param elements the {@code Iterable} to add to the {@code ImmutableMultiset}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null element
*/
@CanIgnoreReturnValue
@Override
public Builder addAll(Iterable elements) {
if (elements instanceof Multiset) {
Multiset multiset = Multisets.cast(elements);
multiset.forEachEntry((e, n) -> contents.add(checkNotNull(e), n));
} else {
super.addAll(elements);
}
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableMultiset}.
*
* @param elements the elements to add to the {@code ImmutableMultiset}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null element
*/
@CanIgnoreReturnValue
@Override
public Builder addAll(Iterator elements) {
super.addAll(elements);
return this;
}
/**
* Returns a newly-created {@code ImmutableMultiset} based on the contents of the {@code
* Builder}.
*/
@Override
public ImmutableMultiset build() {
return copyOf(contents);
}
@VisibleForTesting
ImmutableMultiset buildJdkBacked() {
if (contents.isEmpty()) {
return of();
}
return JdkBackedImmutableMultiset.create(contents.entrySet());
}
}
static final class ElementSet extends ImmutableSet.Indexed {
private final List> entries;
// TODO(cpovirk): @Weak?
private final Multiset delegate;
ElementSet(List> entries, Multiset delegate) {
this.entries = entries;
this.delegate = delegate;
}
@Override
E get(int index) {
return entries.get(index).getElement();
}
@Override
public boolean contains(@CheckForNull Object object) {
return delegate.contains(object);
}
@Override
boolean isPartialView() {
return true;
}
@Override
public int size() {
return entries.size();
}
}
@J2ktIncompatible
static final class SerializedForm implements Serializable {
final Object[] elements;
final int[] counts;
// "extends Object" works around https://github.com/typetools/checker-framework/issues/3013
SerializedForm(Multiset multiset) {
int distinct = multiset.entrySet().size();
elements = new Object[distinct];
counts = new int[distinct];
int i = 0;
for (Entry entry : multiset.entrySet()) {
elements[i] = entry.getElement();
counts[i] = entry.getCount();
i++;
}
}
Object readResolve() {
LinkedHashMultiset