/*
* Copyright (C) 2008 Google Inc.
*
* 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 com.google.common.annotations.GwtCompatible;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.collect.Serialization.FieldSetter;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
/**
* An immutable hash-based multiset. Does not permit null elements.
*
* <p>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.
*
* @author Jared Levy
* @since 2010.01.04 <b>stable</b> (imported from Google Collections Library)
*/
@GwtCompatible(serializable = true)
public class ImmutableMultiset<E> extends ImmutableCollection<E>
implements Multiset<E> {
/**
* Returns the empty immutable multiset.
*/
@SuppressWarnings("unchecked") // all supported methods are covariant
public static <E> ImmutableMultiset<E> of() {
// BEGIN android-changed
return (ImmutableMultiset) EmptyImmutableMultiset.INSTANCE;
// END android-changed
}
/**
* Returns an immutable multiset containing the given elements.
*
* <p>The multiset is ordered by the first occurrence of each element. For
* example, {@code ImmutableMultiset.of(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
*/
public static <E> ImmutableMultiset<E> of(E... elements) {
return copyOf(Arrays.asList(elements));
}
/**
* Returns an immutable multiset containing the given elements.
*
* <p>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}.
*
* <p>Note that if {@code c} is a {@code Collection<String>}, then {@code
* ImmutableMultiset.copyOf(c)} returns an {@code ImmutableMultiset<String>}
* containing each of the strings in {@code c}, while
* {@code ImmutableMultiset.of(c)} returns an
* {@code ImmutableMultiset<Collection<String>>} containing one element (the
* given collection itself).
*
* <p><b>Note:</b> 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 <E> ImmutableMultiset<E> copyOf(
Iterable<? extends E> elements) {
if (elements instanceof ImmutableMultiset) {
@SuppressWarnings("unchecked") // all supported methods are covariant
ImmutableMultiset<E> result = (ImmutableMultiset<E>) elements;
return result;
}
@SuppressWarnings("unchecked") // the cast causes a warning
Multiset<? extends E> multiset = (elements instanceof Multiset)
? (Multiset<? extends E>) elements
: LinkedHashMultiset.create(elements);
return copyOfInternal(multiset);
}
private static <E> ImmutableMultiset<E> copyOfInternal(
Multiset<? extends E> multiset) {
long size = 0;
ImmutableMap.Builder<E, Integer> builder = ImmutableMap.builder();
for (Entry<? extends E> entry : multiset.entrySet()) {
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 ImmutableMultiset<E>(
builder.build(), (int) Math.min(size, Integer.MAX_VALUE));
}
/**
* Returns an immutable multiset containing the given elements.
*
* <p>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 <E> ImmutableMultiset<E> copyOf(
Iterator<? extends E> elements) {
Multiset<E> multiset = LinkedHashMultiset.create();
Iterators.addAll(multiset, elements);
return copyOfInternal(multiset);
}
private final transient ImmutableMap<E, Integer> map;
private final transient int size;
// These constants allow the deserialization code to set final fields. This
// holder class makes sure they are not initialized unless an instance is
// deserialized.
@SuppressWarnings("unchecked")
// eclipse doesn't like the raw types here, but they're harmless
private static class FieldSettersHolder {
static final FieldSetter<ImmutableMultiset> MAP_FIELD_SETTER
= Serialization.getFieldSetter(ImmutableMultiset.class, "map");
static final FieldSetter<ImmutableMultiset> SIZE_FIELD_SETTER
= Serialization.getFieldSetter(ImmutableMultiset.class, "size");
}
ImmutableMultiset(ImmutableMap<E, Integer> map, int size) {
this.map = map;
this.size = size;
}
public int count(@Nullable Object element) {
Integer value = map.get(element);
return (value == null) ? 0 : value;
}
@Override public UnmodifiableIterator<E> iterator() {
final Iterator<Map.Entry<E, Integer>> mapIterator
= map.entrySet().iterator();
return new UnmodifiableIterator<E>() {
int remaining;
E element;
public boolean hasNext() {
return (remaining > 0) || mapIterator.hasNext();
}
public E next() {
if (remaining <= 0) {
Map.Entry<E, Integer> entry = mapIterator.next();
element = entry.getKey();
remaining = entry.getValue();
}
remaining--;
return element;
}
};
}
public int size() {
return size;
}
@Override public boolean contains(@Nullable Object element) {
return map.containsKey(element);
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
*/
public int add(E element, int occurrences) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
*/
public int remove(Object element, int occurrences) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
*/
public int setCount(E element, int count) {
throw new UnsupportedOperationException();
}
/**
* Guaranteed to throw an exception and leave the collection unmodified.
*
* @throws UnsupportedOperationException always
*/
public boolean setCount(E element, int oldCount, int newCount) {
throw new UnsupportedOperationException();
}
@Override public boolean equals(@Nullable Object object) {
if (object == this) {
return true;
}
if (object instanceof Multiset) {
Multiset<?> that = (Multiset<?>) object;
if (this.size() != that.size()) {
return false;
}
for (Entry<?> entry : that.entrySet()) {
if (count(entry.getElement()) != entry.getCount()) {
return false;
}
}
return true;
}
return false;
}
@Override public int hashCode() {
// could cache this, but not considered worthwhile to do so
return map.hashCode();
}
@Override public String toString() {
return entrySet().toString();
}
// TODO: Serialization of the element set should serialize the multiset, and
// deserialization should call multiset.elementSet(). Then
// reserialized(multiset).elementSet() == reserialized(multiset.elementSet())
// Currently, those object references differ.
public Set<E> elementSet() {
return map.keySet();
}
private transient ImmutableSet<Entry<E>> entrySet;
public Set<Entry<E>> entrySet() {
ImmutableSet<Entry<E>> es = entrySet;
return (es == null) ? (entrySet = new EntrySet<E>(this)) : es;
}
private static class EntrySet<E> extends ImmutableSet<Entry<E>> {
final ImmutableMultiset<E> multiset;
public EntrySet(ImmutableMultiset<E> multiset) {
this.multiset = multiset;
}
@Override public UnmodifiableIterator<Entry<E>> iterator() {
final Iterator<Map.Entry<E, Integer>> mapIterator
= multiset.map.entrySet().iterator();
return new UnmodifiableIterator<Entry<E>>() {
public boolean hasNext() {
return mapIterator.hasNext();
}
public Entry<E> next() {
Map.Entry<E, Integer> mapEntry = mapIterator.next();
return
Multisets.immutableEntry(mapEntry.getKey(), mapEntry.getValue());
}
};
}
public int size() {
return multiset.map.size();
}
@Override public boolean contains(Object o) {
if (o instanceof Entry) {
Entry<?> entry = (Entry<?>) o;
if (entry.getCount() <= 0) {
return false;
}
int count = multiset.count(entry.getElement());
return count == entry.getCount();
}
return false;
}
@Override public int hashCode() {
return multiset.map.hashCode();
}
@Override Object writeReplace() {
return this;
}
private static final long serialVersionUID = 0;
}
/**
* @serialData the number of distinct elements, the first element, its count,
* the second element, its count, and so on
*/
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
Serialization.writeMultiset(this, stream);
}
private void readObject(ObjectInputStream stream)
throws IOException, ClassNotFoundException {
stream.defaultReadObject();
int entryCount = stream.readInt();
ImmutableMap.Builder<E, Integer> builder = ImmutableMap.builder();
long tmpSize = 0;
for (int i = 0; i < entryCount; i++) {
@SuppressWarnings("unchecked") // reading data stored by writeMultiset
E element = (E) stream.readObject();
int count = stream.readInt();
if (count <= 0) {
throw new InvalidObjectException("Invalid count " + count);
}
builder.put(element, count);
tmpSize += count;
}
FieldSettersHolder.MAP_FIELD_SETTER.set(this, builder.build());
FieldSettersHolder.SIZE_FIELD_SETTER.set(
this, (int) Math.min(tmpSize, Integer.MAX_VALUE));
}
@Override Object writeReplace() {
return this;
}
private static final long serialVersionUID = 0;
/**
* Returns a new builder. The generated builder is equivalent to the builder
* created by the {@link Builder} constructor.
*/
public static <E> Builder<E> builder() {
return new Builder<E>();
}
/**
* A builder for creating immutable multiset instances, especially
* {@code public static final} multisets ("constant multisets").
*
* <p>Example:
* <pre> {@code
* public static final ImmutableMultiset<Bean> BEANS
* = new ImmutableMultiset.Builder<Bean>()
* .addCopies(Bean.COCOA, 4)
* .addCopies(Bean.GARDEN, 6)
* .addCopies(Bean.RED, 8)
* .addCopies(Bean.BLACK_EYED, 10)
* .build();}</pre>
*
* <p>Builder instances can be reused - it is safe to call {@link #build}
* multiple times to build multiple multisets in series. Each multiset
* is a superset of the multiset created before it.
*/
public static final class Builder<E> extends ImmutableCollection.Builder<E> {
private final Multiset<E> contents = LinkedHashMultiset.create();
/**
* Creates a new builder. The returned builder is equivalent to the builder
* generated by {@link ImmutableMultiset#builder}.
*/
public Builder() {}
/**
* 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<E> 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<E> 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<E> 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<E> 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<E> addAll(Iterable<? extends E> elements) {
if (elements instanceof Multiset) {
@SuppressWarnings("unchecked")
Multiset<? extends E> multiset = (Multiset<? extends E>) elements;
for (Entry<? extends E> 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<E> addAll(Iterator<? extends E> elements) {
super.addAll(elements);
return this;
}
/**
* Returns a newly-created {@code ImmutableMultiset} based on the contents
* of the {@code Builder}.
*/
@Override public ImmutableMultiset<E> build() {
return copyOf(contents);
}
}
}