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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 com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.Multiset.Entry;
import com.google.common.primitives.Ints;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import javax.annotation.Nullable;
/**
* An immutable hash-based multiset. Does not permit null elements.
*
* Its iterator orders elements according to the first appearance of the
* element among the items passed to the factory method or builder. When the
* multiset contains multiple instances of an element, those instances are
* consecutive in the iteration order.
*
*
See the Guava User Guide article on
* immutable collections .
*
* @author Jared Levy
* @author Louis Wasserman
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // we're overriding default serialization
// TODO(user): write an efficient asList() implementation
public abstract class ImmutableMultiset extends ImmutableCollection
implements Multiset {
private static final ImmutableMultiset EMPTY =
new RegularImmutableMultiset(ImmutableMap.of(), 0);
/**
* Returns the empty immutable multiset.
*/
@SuppressWarnings("unchecked") // all supported methods are covariant
public static ImmutableMultiset of() {
return (ImmutableMultiset) EMPTY;
}
/**
* Returns an immutable multiset containing a single element.
*
* @throws NullPointerException if {@code element} is null
* @since 6.0 (source-compatible since 2.0)
*/
@SuppressWarnings("unchecked") // generic array created but never written
public static ImmutableMultiset of(E element) {
return copyOfInternal(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)
*/
@SuppressWarnings("unchecked") //
public static ImmutableMultiset of(E e1, E e2) {
return copyOfInternal(e1, e2);
}
/**
* 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)
*/
@SuppressWarnings("unchecked") //
public static ImmutableMultiset of(E e1, E e2, E e3) {
return copyOfInternal(e1, e2, e3);
}
/**
* 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)
*/
@SuppressWarnings("unchecked") //
public static ImmutableMultiset of(E e1, E e2, E e3, E e4) {
return copyOfInternal(e1, e2, e3, e4);
}
/**
* 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)
*/
@SuppressWarnings("unchecked") //
public static ImmutableMultiset of(E e1, E e2, E e3, E e4, E e5) {
return copyOfInternal(e1, e2, e3, e4, e5);
}
/**
* 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)
*/
@SuppressWarnings("unchecked") //
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.
*
* The multiset is ordered by the first occurrence of each element. For
* example, {@code ImmutableMultiset.copyOf([2, 3, 1, 3])} yields a multiset
* with elements in the order {@code 2, 3, 3, 1}.
*
* @throws NullPointerException if any of {@code elements} is null
* @since 6.0
*/
public static ImmutableMultiset copyOf(E[] elements) {
return copyOf(Arrays.asList(elements));
}
/**
* Returns an immutable multiset containing the given elements.
*
* The multiset is ordered by the first occurrence of each element. For
* example, {@code ImmutableMultiset.copyOf(Arrays.asList(2, 3, 1, 3))} yields
* a multiset with elements in the order {@code 2, 3, 3, 1}.
*
*
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.
*
*
Note: Despite what the method name suggests, if {@code elements}
* is an {@code ImmutableMultiset}, no copy will actually be performed, and
* the given multiset itself will be returned.
*
* @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 copyOfInternal(multiset);
}
private static ImmutableMultiset copyOfInternal(E... elements) {
return copyOf(Arrays.asList(elements));
}
private static ImmutableMultiset copyOfInternal(
Multiset multiset) {
return copyFromEntries(multiset.entrySet());
}
static ImmutableMultiset copyFromEntries(
Collection> entries) {
long size = 0;
ImmutableMap.Builder builder = ImmutableMap.builder();
for (Entry entry : entries) {
int count = entry.getCount();
if (count > 0) {
// Since ImmutableMap.Builder throws an NPE if an element is null, no
// other null checks are needed.
builder.put(entry.getElement(), count);
size += count;
}
}
if (size == 0) {
return of();
}
return new RegularImmutableMultiset(
builder.build(), Ints.saturatedCast(size));
}
/**
* Returns an immutable multiset containing the given elements.
*
* The multiset is ordered by the first occurrence of each element. For
* example,
* {@code ImmutableMultiset.copyOf(Arrays.asList(2, 3, 1, 3).iterator())}
* yields a multiset with elements in the order {@code 2, 3, 3, 1}.
*
* @throws NullPointerException if any of {@code elements} is null
*/
public static ImmutableMultiset copyOf(
Iterator elements) {
Multiset multiset = LinkedHashMultiset.create();
Iterators.addAll(multiset, elements);
return copyOfInternal(multiset);
}
ImmutableMultiset() {}
@Override public UnmodifiableIterator iterator() {
final Iterator> entryIterator = entrySet().iterator();
return new UnmodifiableIterator() {
int remaining;
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--;
return element;
}
};
}
@Override
public boolean contains(@Nullable Object object) {
return count(object) > 0;
}
@Override
public boolean containsAll(Collection targets) {
return elementSet().containsAll(targets);
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
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.
*/
@Deprecated
@Override
public final int remove(Object element, int occurrences) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
* @deprecated Unsupported operation.
*/
@Deprecated
@Override
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.
*/
@Deprecated
@Override
public final boolean setCount(E element, int oldCount, int newCount) {
throw new UnsupportedOperationException();
}
@GwtIncompatible("not present in emulated superclass")
@Override
int copyIntoArray(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(@Nullable Object object) {
return Multisets.equalsImpl(this, object);
}
@Override public int hashCode() {
return Sets.hashCodeImpl(entrySet());
}
@Override public String toString() {
return entrySet().toString();
}
private transient ImmutableSet> entrySet;
@Override
public ImmutableSet> entrySet() {
ImmutableSet> es = entrySet;
return (es == null) ? (entrySet = createEntrySet()) : es;
}
private final ImmutableSet> createEntrySet() {
return isEmpty() ? ImmutableSet.>of() : new EntrySet();
}
abstract Entry getEntry(int index);
private final class EntrySet extends ImmutableSet> {
@Override
boolean isPartialView() {
return ImmutableMultiset.this.isPartialView();
}
@Override
public UnmodifiableIterator> iterator() {
return asList().iterator();
}
@Override
ImmutableList> createAsList() {
return new ImmutableAsList>() {
@Override
public Entry get(int index) {
return getEntry(index);
}
@Override
ImmutableCollection> delegateCollection() {
return EntrySet.this;
}
};
}
@Override
public int size() {
return elementSet().size();
}
@Override
public boolean contains(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();
}
// We can't label this with @Override, because it doesn't override anything
// in the GWT emulated version.
// TODO(cpovirk): try making all copies of this method @GwtIncompatible instead
Object writeReplace() {
return new EntrySetSerializedForm(ImmutableMultiset.this);
}
private static final long serialVersionUID = 0;
}
static class EntrySetSerializedForm implements Serializable {
final ImmutableMultiset multiset;
EntrySetSerializedForm(ImmutableMultiset multiset) {
this.multiset = multiset;
}
Object readResolve() {
return multiset.entrySet();
}
}
private static class SerializedForm implements Serializable {
final Object[] elements;
final int[] counts;
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 multiset =
LinkedHashMultiset.create(elements.length);
for (int i = 0; i < elements.length; i++) {
multiset.add(elements[i], counts[i]);
}
return ImmutableMultiset.copyOf(multiset);
}
private static final long serialVersionUID = 0;
}
// We can't label this with @Override, because it doesn't override anything
// in the GWT emulated version.
Object writeReplace() {
return new SerializedForm(this);
}
/**
* 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 (imported from Google Collections Library)
*/
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
*/
@Override public Builder add(E element) {
contents.add(checkNotNull(element));
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
*/
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
*/
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 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 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
*/
@Override public Builder addAll(Iterable elements) {
if (elements instanceof Multiset) {
Multiset multiset = Multisets.cast(elements);
for (Entry entry : multiset.entrySet()) {
addCopies(entry.getElement(), entry.getCount());
}
} 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
*/
@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);
}
}
}
