com.google.common.collect.AbstractMultiset Maven / Gradle / Ivy
/*
* 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.collect.Multisets.setCountImpl;
import com.google.common.annotations.GwtCompatible;
import java.util.AbstractCollection;
import java.util.Collection;
import java.util.Iterator;
import java.util.Set;
/**
* This class provides a skeletal implementation of the {@link Multiset} interface. A new multiset
* implementation can be created easily by extending this class and implementing the {@link
* Multiset#entrySet()} method, plus optionally overriding {@link #add(Object, int)} and {@link
* #remove(Object, int)} to enable modifications to the multiset.
*
* The {@link #count} and {@link #size} implementations all iterate across the set returned by
* {@link Multiset#entrySet()}, as do many methods acting on the set returned by {@link
* #elementSet()}. Override those methods for better performance.
*
* @author Kevin Bourrillion
* @author Louis Wasserman
*/
@GwtCompatible
abstract class AbstractMultiset extends AbstractCollection implements Multiset {
// Query Operations
@Override
public boolean isEmpty() {
return entrySet().isEmpty();
}
@Override
public boolean contains(Object element) {
return count(element) > 0;
}
// Modification Operations
@Override
public final boolean add(E element) {
add(element, 1);
return true;
}
@Override
public int add(E element, int occurrences) {
throw new UnsupportedOperationException();
}
@Override
public final boolean remove(Object element) {
return remove(element, 1) > 0;
}
@Override
public int remove(Object element, int occurrences) {
throw new UnsupportedOperationException();
}
@Override
public int setCount(E element, int count) {
return setCountImpl(this, element, count);
}
@Override
public boolean setCount(E element, int oldCount, int newCount) {
return setCountImpl(this, element, oldCount, newCount);
}
// Bulk Operations
/**
* {@inheritDoc}
*
* This implementation is highly efficient when {@code elementsToAdd} is itself a {@link
* Multiset}.
*/
@Override
public final boolean addAll(Collection elementsToAdd) {
return Multisets.addAllImpl(this, elementsToAdd);
}
@Override
public final boolean removeAll(Collection elementsToRemove) {
return Multisets.removeAllImpl(this, elementsToRemove);
}
@Override
public final boolean retainAll(Collection elementsToRetain) {
return Multisets.retainAllImpl(this, elementsToRetain);
}
@Override
public abstract void clear();
// Views
private transient Set elementSet;
@Override
public Set elementSet() {
Set result = elementSet;
if (result == null) {
elementSet = result = createElementSet();
}
return result;
}
/**
* Creates a new instance of this multiset's element set, which will be returned by {@link
* #elementSet()}.
*/
Set createElementSet() {
return new ElementSet();
}
class ElementSet extends Multisets.ElementSet {
@Override
Multiset multiset() {
return AbstractMultiset.this;
}
@Override
public Iterator iterator() {
return elementIterator();
}
}
abstract Iterator elementIterator();
private transient Set> entrySet;
@Override
public Set> entrySet() {
Set> result = entrySet;
if (result == null) {
entrySet = result = createEntrySet();
}
return result;
}
class EntrySet extends Multisets.EntrySet {
@Override
Multiset multiset() {
return AbstractMultiset.this;
}
@Override
public Iterator> iterator() {
return entryIterator();
}
@Override
public int size() {
return distinctElements();
}
}
Set> createEntrySet() {
return new EntrySet();
}
abstract Iterator> entryIterator();
abstract int distinctElements();
// Object methods
/**
* {@inheritDoc}
*
* This implementation returns {@code true} if {@code object} is a multiset of the same size
* and if, for each element, the two multisets have the same count.
*/
@Override
public final boolean equals(Object object) {
return Multisets.equalsImpl(this, object);
}
/**
* {@inheritDoc}
*
*
This implementation returns the hash code of {@link Multiset#entrySet()}.
*/
@Override
public final int hashCode() {
return entrySet().hashCode();
}
/**
* {@inheritDoc}
*
*
This implementation returns the result of invoking {@code toString} on {@link
* Multiset#entrySet()}.
*/
@Override
public final String toString() {
return entrySet().toString();
}
}