com.google.common.collect.ForwardingSortedMultiset Maven / Gradle / Ivy
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/*
* 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NavigableSet;
/**
* A sorted multiset which forwards all its method calls to another sorted multiset. Subclasses
* should override one or more methods to modify the behavior of the backing multiset as desired
* per the decorator pattern.
*
* Warning: The methods of {@code ForwardingSortedMultiset} forward
* indiscriminately to the methods of the delegate. For example, overriding
* {@link #add(Object, int)} alone will not change the behavior of {@link #add(Object)},
* which can lead to unexpected behavior. In this case, you should override {@code add(Object)} as
* well, either providing your own implementation, or delegating to the provided {@code
* standardAdd} method.
*
*
The {@code standard} methods and any collection views they return are not guaranteed to be
* thread-safe, even when all of the methods that they depend on are thread-safe.
*
* @author Louis Wasserman
* @since 15.0
*/
@Beta
@GwtCompatible(emulated = true)
public abstract class ForwardingSortedMultiset extends ForwardingMultiset
implements SortedMultiset {
/** Constructor for use by subclasses. */
protected ForwardingSortedMultiset() {}
@Override
protected abstract SortedMultiset delegate();
@Override
public NavigableSet elementSet() {
return (NavigableSet) super.elementSet();
}
/**
* A sensible implementation of {@link SortedMultiset#elementSet} in terms of the following
* methods: {@link SortedMultiset#clear}, {@link SortedMultiset#comparator}, {@link
* SortedMultiset#contains}, {@link SortedMultiset#containsAll}, {@link SortedMultiset#count},
* {@link SortedMultiset#firstEntry} {@link SortedMultiset#headMultiset}, {@link
* SortedMultiset#isEmpty}, {@link SortedMultiset#lastEntry}, {@link SortedMultiset#subMultiset},
* {@link SortedMultiset#tailMultiset}, the {@code size()} and {@code iterator()} methods of
* {@link SortedMultiset#entrySet}, and {@link SortedMultiset#remove(Object, int)}. In many
* situations, you may wish to override {@link SortedMultiset#elementSet} to forward to this
* implementation or a subclass thereof.
*/
protected class StandardElementSet extends SortedMultisets.NavigableElementSet {
/** Constructor for use by subclasses. */
public StandardElementSet() {
super(ForwardingSortedMultiset.this);
}
}
@Override
public Comparator comparator() {
return delegate().comparator();
}
@Override
public SortedMultiset descendingMultiset() {
return delegate().descendingMultiset();
}
/**
* A skeleton implementation of a descending multiset view. Normally,
* {@link #descendingMultiset()} will not reflect any changes you make to the behavior of methods
* such as {@link #add(Object)} or {@link #pollFirstEntry}. This skeleton implementation
* correctly delegates each of its operations to the appropriate methods of this {@code
* ForwardingSortedMultiset}.
*
* In many cases, you may wish to override {@link #descendingMultiset()} to return an instance of
* a subclass of {@code StandardDescendingMultiset}.
*/
protected abstract class StandardDescendingMultiset
extends DescendingMultiset {
/** Constructor for use by subclasses. */
public StandardDescendingMultiset() {}
@Override
SortedMultiset forwardMultiset() {
return ForwardingSortedMultiset.this;
}
}
@Override
public Entry firstEntry() {
return delegate().firstEntry();
}
/**
* A sensible definition of {@link #firstEntry()} in terms of {@code entrySet().iterator()}.
*
* If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to forward
* to this implementation.
*/
protected Entry standardFirstEntry() {
Iterator> entryIterator = entrySet().iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry entry = entryIterator.next();
return Multisets.immutableEntry(entry.getElement(), entry.getCount());
}
@Override
public Entry lastEntry() {
return delegate().lastEntry();
}
/**
* A sensible definition of {@link #lastEntry()} in terms of {@code
* descendingMultiset().entrySet().iterator()}.
*
* If you override {@link #descendingMultiset} or {@link #entrySet()}, you may wish to override
* {@link #firstEntry()} to forward to this implementation.
*/
protected Entry standardLastEntry() {
Iterator> entryIterator = descendingMultiset()
.entrySet()
.iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry entry = entryIterator.next();
return Multisets.immutableEntry(entry.getElement(), entry.getCount());
}
@Override
public Entry pollFirstEntry() {
return delegate().pollFirstEntry();
}
/**
* A sensible definition of {@link #pollFirstEntry()} in terms of {@code entrySet().iterator()}.
*
* If you override {@link #entrySet()}, you may wish to override {@link #pollFirstEntry()} to
* forward to this implementation.
*/
protected Entry standardPollFirstEntry() {
Iterator> entryIterator = entrySet().iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry entry = entryIterator.next();
entry = Multisets.immutableEntry(entry.getElement(), entry.getCount());
entryIterator.remove();
return entry;
}
@Override
public Entry pollLastEntry() {
return delegate().pollLastEntry();
}
/**
* A sensible definition of {@link #pollLastEntry()} in terms of {@code
* descendingMultiset().entrySet().iterator()}.
*
* If you override {@link #descendingMultiset()} or {@link #entrySet()}, you may wish to override
* {@link #pollLastEntry()} to forward to this implementation.
*/
protected Entry standardPollLastEntry() {
Iterator> entryIterator = descendingMultiset()
.entrySet()
.iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry entry = entryIterator.next();
entry = Multisets.immutableEntry(entry.getElement(), entry.getCount());
entryIterator.remove();
return entry;
}
@Override
public SortedMultiset headMultiset(E upperBound, BoundType boundType) {
return delegate().headMultiset(upperBound, boundType);
}
@Override
public SortedMultiset subMultiset(
E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType) {
return delegate().subMultiset(lowerBound, lowerBoundType, upperBound, upperBoundType);
}
/**
* A sensible definition of {@link #subMultiset(Object, BoundType, Object, BoundType)} in terms
* of {@link #headMultiset(Object, BoundType) headMultiset} and
* {@link #tailMultiset(Object, BoundType) tailMultiset}.
*
* If you override either of these methods, you may wish to override
* {@link #subMultiset(Object, BoundType, Object, BoundType)} to forward to this implementation.
*/
protected SortedMultiset standardSubMultiset(
E lowerBound, BoundType lowerBoundType, E upperBound, BoundType upperBoundType) {
return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
}
@Override
public SortedMultiset tailMultiset(E lowerBound, BoundType boundType) {
return delegate().tailMultiset(lowerBound, boundType);
}
}