com.google.common.collect.ImmutableSortedMultiset Maven / Gradle / Ivy
/*
* Copyright (C) 2011 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtIncompatible;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
/**
* An immutable {@code SortedMultiset} that stores its elements in a sorted array. Some instances
* are ordered by an explicit comparator, while others follow the natural sort ordering of their
* elements. Either way, null elements are not supported.
*
* Unlike {@link Multisets#unmodifiableSortedMultiset}, which is a view of a separate
* collection that can still change, an instance of {@code ImmutableSortedMultiset} contains its
* own private data and will never change. This class is convenient for {@code public static
* final} multisets ("constant multisets") and also lets you easily make a "defensive copy" of a
* set provided to your class by a caller.
*
*
The multisets returned by the {@link #headMultiset}, {@link #tailMultiset}, and
* {@link #subMultiset} methods share the same array as the original multiset, preventing that
* array from being garbage collected. If this is a concern, the data may be copied into a
* correctly-sized array by calling {@link #copyOfSorted}.
*
*
Note on element equivalence: The {@link #contains(Object)},
* {@link #containsAll(Collection)}, and {@link #equals(Object)} implementations must check whether
* a provided object is equivalent to an element in the collection. Unlike most collections, an
* {@code ImmutableSortedMultiset} doesn't use {@link Object#equals} to determine if two elements
* are equivalent. Instead, with an explicit comparator, the following relation determines whether
* elements {@code x} and {@code y} are equivalent:
*
*
{@code
*
* {(x, y) | comparator.compare(x, y) == 0}}
*
* With natural ordering of elements, the following relation determines whether two elements are
* equivalent:
*
*
{@code
*
* {(x, y) | x.compareTo(y) == 0}}
*
* Warning: Like most multisets, an {@code ImmutableSortedMultiset} will not function
* correctly if an element is modified after being placed in the multiset. For this reason, and to
* avoid general confusion, it is strongly recommended to place only immutable objects into this
* collection.
*
* Note: Although this class is not final, it cannot be subclassed as it has no public or
* protected constructors. Thus, instances of this type are guaranteed to be immutable.
*
*
See the Guava User Guide article on
* immutable collections.
*
* @author Louis Wasserman
* @since 12.0
*/
@Beta
@GwtIncompatible("hasn't been tested yet")
public abstract class ImmutableSortedMultiset extends ImmutableSortedMultisetFauxverideShim
implements SortedMultiset {
// TODO(user): GWT compatibility
private static final Comparator NATURAL_ORDER = Ordering.natural();
private static final ImmutableSortedMultiset NATURAL_EMPTY_MULTISET =
new EmptyImmutableSortedMultiset(NATURAL_ORDER);
/**
* Returns the empty immutable sorted multiset.
*/
@SuppressWarnings("unchecked")
public static ImmutableSortedMultiset of() {
return (ImmutableSortedMultiset) NATURAL_EMPTY_MULTISET;
}
/**
* Returns an immutable sorted multiset containing a single element.
*/
public static > ImmutableSortedMultiset of(E element) {
RegularImmutableSortedSet elementSet =
(RegularImmutableSortedSet) ImmutableSortedSet.of(element);
int[] counts = {1};
long[] cumulativeCounts = {0, 1};
return new RegularImmutableSortedMultiset(elementSet, counts, cumulativeCounts, 0, 1);
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering.
*
* @throws NullPointerException if any element is null
*/
@SuppressWarnings("unchecked")
public static > ImmutableSortedMultiset of(E e1, E e2) {
return copyOf(Ordering.natural(), Arrays.asList(e1, e2));
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering.
*
* @throws NullPointerException if any element is null
*/
@SuppressWarnings("unchecked")
public static > ImmutableSortedMultiset of(E e1, E e2, E e3) {
return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3));
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering.
*
* @throws NullPointerException if any element is null
*/
@SuppressWarnings("unchecked")
public static > ImmutableSortedMultiset of(
E e1, E e2, E e3, E e4) {
return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3, e4));
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering.
*
* @throws NullPointerException if any element is null
*/
@SuppressWarnings("unchecked")
public static > ImmutableSortedMultiset of(
E e1, E e2, E e3, E e4, E e5) {
return copyOf(Ordering.natural(), Arrays.asList(e1, e2, e3, e4, e5));
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering.
*
* @throws NullPointerException if any element is null
*/
@SuppressWarnings("unchecked")
public static > ImmutableSortedMultiset of(
E e1, E e2, E e3, E e4, E e5, E e6, E... remaining) {
int size = remaining.length + 6;
List all = Lists.newArrayListWithCapacity(size);
Collections.addAll(all, e1, e2, e3, e4, e5, e6);
Collections.addAll(all, remaining);
return copyOf(Ordering.natural(), all);
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static > ImmutableSortedMultiset copyOf(E[] elements) {
return copyOf(Ordering.natural(), Arrays.asList(elements));
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering. To create a copy of a {@code SortedMultiset} that preserves the
* comparator, call {@link #copyOfSorted} instead. This method iterates over {@code elements} at
* most once.
*
* Note that if {@code s} is a {@code multiset}, then {@code
* ImmutableSortedMultiset.copyOf(s)} returns an {@code ImmutableSortedMultiset}
* containing each of the strings in {@code s}, while {@code ImmutableSortedMultiset.of(s)}
* returns an {@code ImmutableSortedMultiset>} containing one element (the given
* multiset itself).
*
* Despite the method name, this method attempts to avoid actually copying the data when it is
* safe to do so. The exact circumstances under which a copy will or will not be performed are
* undocumented and subject to change.
*
*
This method is not type-safe, as it may be called on elements that are not mutually
* comparable.
*
* @throws ClassCastException if the elements are not mutually comparable
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableSortedMultiset copyOf(Iterable elements) {
// Hack around E not being a subtype of Comparable.
// Unsafe, see ImmutableSortedMultisetFauxverideShim.
@SuppressWarnings("unchecked")
Ordering naturalOrder = (Ordering) Ordering.natural();
return copyOf(naturalOrder, elements);
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by their natural
* ordering.
*
* This method is not type-safe, as it may be called on elements that are not mutually
* comparable.
*
* @throws ClassCastException if the elements are not mutually comparable
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableSortedMultiset copyOf(Iterator elements) {
// Hack around E not being a subtype of Comparable.
// Unsafe, see ImmutableSortedMultisetFauxverideShim.
@SuppressWarnings("unchecked")
Ordering naturalOrder = (Ordering) Ordering.natural();
return copyOf(naturalOrder, elements);
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by the given {@code
* Comparator}.
*
* @throws NullPointerException if {@code comparator} or any of {@code elements} is null
*/
public static ImmutableSortedMultiset copyOf(
Comparator comparator, Iterator elements) {
checkNotNull(comparator);
return new Builder(comparator).addAll(elements).build();
}
/**
* Returns an immutable sorted multiset containing the given elements sorted by the given {@code
* Comparator}. This method iterates over {@code elements} at most once.
*
* Despite the method name, this method attempts to avoid actually copying the data when it is
* safe to do so. The exact circumstances under which a copy will or will not be performed are
* undocumented and subject to change.
*
* @throws NullPointerException if {@code comparator} or any of {@code elements} is null
*/
public static ImmutableSortedMultiset copyOf(
Comparator comparator, Iterable elements) {
if (elements instanceof ImmutableSortedMultiset) {
@SuppressWarnings("unchecked") // immutable collections are always safe for covariant casts
ImmutableSortedMultiset multiset = (ImmutableSortedMultiset) elements;
if (comparator.equals(multiset.comparator())) {
if (multiset.isPartialView()) {
return copyOfSortedEntries(comparator, multiset.entrySet().asList());
} else {
return multiset;
}
}
}
elements = Lists.newArrayList(elements); // defensive copy
TreeMultiset sortedCopy = TreeMultiset.create(checkNotNull(comparator));
Iterables.addAll(sortedCopy, elements);
return copyOfSortedEntries(comparator, sortedCopy.entrySet());
}
/**
* Returns an immutable sorted multiset containing the elements of a sorted multiset, sorted by
* the same {@code Comparator}. That behavior differs from {@link #copyOf(Iterable)}, which
* always uses the natural ordering of the elements.
*
* Despite the method name, this method attempts to avoid actually copying the data when it is
* safe to do so. The exact circumstances under which a copy will or will not be performed are
* undocumented and subject to change.
*
*
This method is safe to use even when {@code sortedMultiset} is a synchronized or concurrent
* collection that is currently being modified by another thread.
*
* @throws NullPointerException if {@code sortedMultiset} or any of its elements is null
*/
public static ImmutableSortedMultiset copyOfSorted(SortedMultiset sortedMultiset) {
return copyOfSortedEntries(sortedMultiset.comparator(),
Lists.newArrayList(sortedMultiset.entrySet()));
}
private static ImmutableSortedMultiset copyOfSortedEntries(
Comparator comparator, Collection> entries) {
if (entries.isEmpty()) {
return emptyMultiset(comparator);
}
ImmutableList.Builder elementsBuilder = new ImmutableList.Builder(entries.size());
int[] counts = new int[entries.size()];
long[] cumulativeCounts = new long[entries.size() + 1];
int i = 0;
for (Entry entry : entries) {
elementsBuilder.add(entry.getElement());
counts[i] = entry.getCount();
cumulativeCounts[i + 1] = cumulativeCounts[i] + counts[i];
i++;
}
return new RegularImmutableSortedMultiset(
new RegularImmutableSortedSet(elementsBuilder.build(), comparator),
counts, cumulativeCounts, 0, entries.size());
}
@SuppressWarnings("unchecked")
static ImmutableSortedMultiset emptyMultiset(Comparator comparator) {
if (NATURAL_ORDER.equals(comparator)) {
return (ImmutableSortedMultiset) NATURAL_EMPTY_MULTISET;
}
return new EmptyImmutableSortedMultiset(comparator);
}
ImmutableSortedMultiset() {}
@Override
public final Comparator comparator() {
return elementSet().comparator();
}
@Override
public abstract ImmutableSortedSet elementSet();
transient ImmutableSortedMultiset descendingMultiset;
@Override
public ImmutableSortedMultiset descendingMultiset() {
ImmutableSortedMultiset result = descendingMultiset;
if (result == null) {
return descendingMultiset = new DescendingImmutableSortedMultiset(this);
}
return result;
}
/**
* {@inheritDoc}
*
* This implementation is guaranteed to throw an {@link UnsupportedOperationException}.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final Entry pollFirstEntry() {
throw new UnsupportedOperationException();
}
/**
* {@inheritDoc}
*
* This implementation is guaranteed to throw an {@link UnsupportedOperationException}.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
public final Entry pollLastEntry() {
throw new UnsupportedOperationException();
}
@Override
public abstract ImmutableSortedMultiset headMultiset(E upperBound, BoundType boundType);
@Override
public ImmutableSortedMultiset subMultiset(
E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType) {
checkArgument(comparator().compare(lowerBound, upperBound) <= 0,
"Expected lowerBound <= upperBound but %s > %s", lowerBound, upperBound);
return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
}
@Override
public abstract ImmutableSortedMultiset tailMultiset(E lowerBound, BoundType boundType);
/**
* Returns a builder that creates immutable sorted multisets with an explicit comparator. If the
* comparator has a more general type than the set being generated, such as creating a {@code
* SortedMultiset} with a {@code Comparator}, use the {@link Builder}
* constructor instead.
*
* @throws NullPointerException if {@code comparator} is null
*/
public static Builder orderedBy(Comparator comparator) {
return new Builder(comparator);
}
/**
* Returns a builder that creates immutable sorted multisets whose elements are ordered by the
* reverse of their natural ordering.
*
* Note: the type parameter {@code E} extends {@code Comparable} rather than {@code
* Comparable} as a workaround for javac bug 6468354.
*/
public static > Builder reverseOrder() {
return new Builder(Ordering.natural().reverse());
}
/**
* Returns a builder that creates immutable sorted multisets whose elements are ordered by their
* natural ordering. The sorted multisets use {@link Ordering#natural()} as the comparator. This
* method provides more type-safety than {@link #builder}, as it can be called only for classes
* that implement {@link Comparable}.
*
* Note: the type parameter {@code E} extends {@code Comparable} rather than {@code
* Comparable} as a workaround for javac bug 6468354.
*/
public static > Builder naturalOrder() {
return new Builder(Ordering.natural());
}
/**
* A builder for creating immutable multiset instances, especially {@code public static final}
* multisets ("constant multisets"). Example:
*
* {@code
*
* public static final ImmutableSortedMultiset BEANS =
* new ImmutableSortedMultiset.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 12.0
*/
public static class Builder extends ImmutableMultiset.Builder {
/**
* Creates a new builder. The returned builder is equivalent to the builder generated by
* {@link ImmutableSortedMultiset#orderedBy(Comparator)}.
*/
public Builder(Comparator comparator) {
super(TreeMultiset.create(checkNotNull(comparator)));
}
/**
* Adds {@code element} to the {@code ImmutableSortedMultiset}.
*
* @param element the element to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code element} is null
*/
@Override
public Builder add(E element) {
super.add(element);
return this;
}
/**
* Adds a number of occurrences of an element to this {@code ImmutableSortedMultiset}.
*
* @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
*/
@Override
public Builder addCopies(E element, int occurrences) {
super.addCopies(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
*/
@Override
public Builder setCount(E element, int count) {
super.setCount(element, count);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
*
* @param elements the elements to add
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null element
*/
@Override
public Builder add(E... elements) {
super.add(elements);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
*
* @param elements the {@code Iterable} to add to the {@code ImmutableSortedMultiset}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null element
*/
@Override
public Builder addAll(Iterable elements) {
super.addAll(elements);
return this;
}
/**
* Adds each element of {@code elements} to the {@code ImmutableSortedMultiset}.
*
* @param elements the elements to add to the {@code ImmutableSortedMultiset}
* @return this {@code Builder} object
* @throws NullPointerException if {@code elements} is null or contains a null element
*/
@Override
public Builder addAll(Iterator elements) {
super.addAll(elements);
return this;
}
/**
* Returns a newly-created {@code ImmutableSortedMultiset} based on the contents of the {@code
* Builder}.
*/
@Override
public ImmutableSortedMultiset build() {
return copyOfSorted((SortedMultiset) contents);
}
}
private static final class SerializedForm implements Serializable {
Comparator comparator;
E[] elements;
int[] counts;
@SuppressWarnings("unchecked")
SerializedForm(SortedMultiset multiset) {
this.comparator = multiset.comparator();
int n = multiset.entrySet().size();
elements = (E[]) new Object[n];
counts = new int[n];
int i = 0;
for (Entry entry : multiset.entrySet()) {
elements[i] = entry.getElement();
counts[i] = entry.getCount();
i++;
}
}
Object readResolve() {
int n = elements.length;
Builder builder = new Builder(comparator);
for (int i = 0; i < n; i++) {
builder.addCopies(elements[i], counts[i]);
}
return builder.build();
}
}
@Override
Object writeReplace() {
return new SerializedForm(this);
}
}