ForwardingSortedMultiset.java
/*
* 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;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* 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 <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
*
* <p><b>Warning:</b> The methods of {@code ForwardingSortedMultiset} forward
* <b>indiscriminately</b> to the methods of the delegate. For example, overriding {@link
* #add(Object, int)} alone <b>will not</b> 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.
*
* <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
* default} methods. Instead, it inherits their default implementations. When those implementations
* invoke methods, they invoke methods on the {@code ForwardingSortedMultiset}.
*
* <p>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)
@ElementTypesAreNonnullByDefault
public abstract class ForwardingSortedMultiset<E extends @Nullable Object>
extends ForwardingMultiset<E> implements SortedMultiset<E> {
/** Constructor for use by subclasses. */
protected ForwardingSortedMultiset() {}
@Override
protected abstract SortedMultiset<E> delegate();
@Override
public NavigableSet<E> elementSet() {
return delegate().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.
*
* @since 15.0
*/
protected class StandardElementSet extends SortedMultisets.NavigableElementSet<E> {
/** Constructor for use by subclasses. */
public StandardElementSet() {
super(ForwardingSortedMultiset.this);
}
}
@Override
public Comparator<? super E> comparator() {
return delegate().comparator();
}
@Override
public SortedMultiset<E> 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}.
*
* <p>In many cases, you may wish to override {@link #descendingMultiset()} to return an instance
* of a subclass of {@code StandardDescendingMultiset}.
*
* @since 15.0
*/
protected abstract class StandardDescendingMultiset extends DescendingMultiset<E> {
/** Constructor for use by subclasses. */
public StandardDescendingMultiset() {}
@Override
SortedMultiset<E> forwardMultiset() {
return ForwardingSortedMultiset.this;
}
}
@Override
@CheckForNull
public Entry<E> firstEntry() {
return delegate().firstEntry();
}
/**
* A sensible definition of {@link #firstEntry()} in terms of {@code entrySet().iterator()}.
*
* <p>If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to
* forward to this implementation.
*/
@CheckForNull
protected Entry<E> standardFirstEntry() {
Iterator<Entry<E>> entryIterator = entrySet().iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry<E> entry = entryIterator.next();
return Multisets.immutableEntry(entry.getElement(), entry.getCount());
}
@Override
@CheckForNull
public Entry<E> lastEntry() {
return delegate().lastEntry();
}
/**
* A sensible definition of {@link #lastEntry()} in terms of {@code
* descendingMultiset().entrySet().iterator()}.
*
* <p>If you override {@link #descendingMultiset} or {@link #entrySet()}, you may wish to override
* {@link #firstEntry()} to forward to this implementation.
*/
@CheckForNull
protected Entry<E> standardLastEntry() {
Iterator<Entry<E>> entryIterator = descendingMultiset().entrySet().iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry<E> entry = entryIterator.next();
return Multisets.immutableEntry(entry.getElement(), entry.getCount());
}
@Override
@CheckForNull
public Entry<E> pollFirstEntry() {
return delegate().pollFirstEntry();
}
/**
* A sensible definition of {@link #pollFirstEntry()} in terms of {@code entrySet().iterator()}.
*
* <p>If you override {@link #entrySet()}, you may wish to override {@link #pollFirstEntry()} to
* forward to this implementation.
*/
@CheckForNull
protected Entry<E> standardPollFirstEntry() {
Iterator<Entry<E>> entryIterator = entrySet().iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry<E> entry = entryIterator.next();
entry = Multisets.immutableEntry(entry.getElement(), entry.getCount());
entryIterator.remove();
return entry;
}
@Override
@CheckForNull
public Entry<E> pollLastEntry() {
return delegate().pollLastEntry();
}
/**
* A sensible definition of {@link #pollLastEntry()} in terms of {@code
* descendingMultiset().entrySet().iterator()}.
*
* <p>If you override {@link #descendingMultiset()} or {@link #entrySet()}, you may wish to
* override {@link #pollLastEntry()} to forward to this implementation.
*/
@CheckForNull
protected Entry<E> standardPollLastEntry() {
Iterator<Entry<E>> entryIterator = descendingMultiset().entrySet().iterator();
if (!entryIterator.hasNext()) {
return null;
}
Entry<E> entry = entryIterator.next();
entry = Multisets.immutableEntry(entry.getElement(), entry.getCount());
entryIterator.remove();
return entry;
}
@Override
public SortedMultiset<E> headMultiset(@ParametricNullness E upperBound, BoundType boundType) {
return delegate().headMultiset(upperBound, boundType);
}
@Override
public SortedMultiset<E> subMultiset(
@ParametricNullness E lowerBound,
BoundType lowerBoundType,
@ParametricNullness 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}.
*
* <p>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<E> standardSubMultiset(
@ParametricNullness E lowerBound,
BoundType lowerBoundType,
@ParametricNullness E upperBound,
BoundType upperBoundType) {
return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
}
@Override
public SortedMultiset<E> tailMultiset(@ParametricNullness E lowerBound, BoundType boundType) {
return delegate().tailMultiset(lowerBound, boundType);
}
}