ForwardingNavigableSet.java
/*
* Copyright (C) 2012 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.GwtIncompatible;
import java.util.Iterator;
import java.util.NavigableSet;
import java.util.SortedSet;
/**
* A navigable set which forwards all its method calls to another navigable set. Subclasses should
* override one or more methods to modify the behavior of the backing set as desired per the <a
* href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
*
* <p><b>Warning:</b> The methods of {@code ForwardingNavigableSet} forward <i>indiscriminately</i>
* to the methods of the delegate. For example, overriding {@link #add} alone <i>will not</i> change
* the behavior of {@link #addAll}, which can lead to unexpected behavior. In this case, you should
* override {@code addAll} as well, either providing your own implementation, or delegating to the
* provided {@code standardAddAll} 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 ForwardingNavigableSet}.
*
* <p>Each of the {@code standard} methods uses the set's comparator (or the natural ordering of the
* elements, if there is no comparator) to test element equality. As a result, if the comparator is
* not consistent with equals, some of the standard implementations may violate the {@code Set}
* contract.
*
* <p>The {@code standard} methods and the 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 12.0
*/
@GwtIncompatible
public abstract class ForwardingNavigableSet<E> extends ForwardingSortedSet<E>
implements NavigableSet<E> {
/** Constructor for use by subclasses. */
protected ForwardingNavigableSet() {}
@Override
protected abstract NavigableSet<E> delegate();
@Override
public E lower(E e) {
return delegate().lower(e);
}
/**
* A sensible definition of {@link #lower} in terms of the {@code descendingIterator} method of
* {@link #headSet(Object, boolean)}. If you override {@link #headSet(Object, boolean)}, you may
* wish to override {@link #lower} to forward to this implementation.
*/
protected E standardLower(E e) {
return Iterators.getNext(headSet(e, false).descendingIterator(), null);
}
@Override
public E floor(E e) {
return delegate().floor(e);
}
/**
* A sensible definition of {@link #floor} in terms of the {@code descendingIterator} method of
* {@link #headSet(Object, boolean)}. If you override {@link #headSet(Object, boolean)}, you may
* wish to override {@link #floor} to forward to this implementation.
*/
protected E standardFloor(E e) {
return Iterators.getNext(headSet(e, true).descendingIterator(), null);
}
@Override
public E ceiling(E e) {
return delegate().ceiling(e);
}
/**
* A sensible definition of {@link #ceiling} in terms of the {@code iterator} method of {@link
* #tailSet(Object, boolean)}. If you override {@link #tailSet(Object, boolean)}, you may wish to
* override {@link #ceiling} to forward to this implementation.
*/
protected E standardCeiling(E e) {
return Iterators.getNext(tailSet(e, true).iterator(), null);
}
@Override
public E higher(E e) {
return delegate().higher(e);
}
/**
* A sensible definition of {@link #higher} in terms of the {@code iterator} method of {@link
* #tailSet(Object, boolean)}. If you override {@link #tailSet(Object, boolean)}, you may wish to
* override {@link #higher} to forward to this implementation.
*/
protected E standardHigher(E e) {
return Iterators.getNext(tailSet(e, false).iterator(), null);
}
@Override
public E pollFirst() {
return delegate().pollFirst();
}
/**
* A sensible definition of {@link #pollFirst} in terms of the {@code iterator} method. If you
* override {@link #iterator} you may wish to override {@link #pollFirst} to forward to this
* implementation.
*/
protected E standardPollFirst() {
return Iterators.pollNext(iterator());
}
@Override
public E pollLast() {
return delegate().pollLast();
}
/**
* A sensible definition of {@link #pollLast} in terms of the {@code descendingIterator} method.
* If you override {@link #descendingIterator} you may wish to override {@link #pollLast} to
* forward to this implementation.
*/
protected E standardPollLast() {
return Iterators.pollNext(descendingIterator());
}
protected E standardFirst() {
return iterator().next();
}
protected E standardLast() {
return descendingIterator().next();
}
@Override
public NavigableSet<E> descendingSet() {
return delegate().descendingSet();
}
/**
* A sensible implementation of {@link NavigableSet#descendingSet} in terms of the other methods
* of {@link NavigableSet}, notably including {@link NavigableSet#descendingIterator}.
*
* <p>In many cases, you may wish to override {@link ForwardingNavigableSet#descendingSet} to
* forward to this implementation or a subclass thereof.
*
* @since 12.0
*/
@Beta
protected class StandardDescendingSet extends Sets.DescendingSet<E> {
/** Constructor for use by subclasses. */
public StandardDescendingSet() {
super(ForwardingNavigableSet.this);
}
}
@Override
public Iterator<E> descendingIterator() {
return delegate().descendingIterator();
}
@Override
public NavigableSet<E> subSet(
E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
return delegate().subSet(fromElement, fromInclusive, toElement, toInclusive);
}
/**
* A sensible definition of {@link #subSet(Object, boolean, Object, boolean)} in terms of the
* {@code headSet} and {@code tailSet} methods. In many cases, you may wish to override {@link
* #subSet(Object, boolean, Object, boolean)} to forward to this implementation.
*/
@Beta
protected NavigableSet<E> standardSubSet(
E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) {
return tailSet(fromElement, fromInclusive).headSet(toElement, toInclusive);
}
/**
* A sensible definition of {@link #subSet(Object, Object)} in terms of the {@link #subSet(Object,
* boolean, Object, boolean)} method. If you override {@link #subSet(Object, boolean, Object,
* boolean)}, you may wish to override {@link #subSet(Object, Object)} to forward to this
* implementation.
*/
@Override
protected SortedSet<E> standardSubSet(E fromElement, E toElement) {
return subSet(fromElement, true, toElement, false);
}
@Override
public NavigableSet<E> headSet(E toElement, boolean inclusive) {
return delegate().headSet(toElement, inclusive);
}
/**
* A sensible definition of {@link #headSet(Object)} in terms of the {@link #headSet(Object,
* boolean)} method. If you override {@link #headSet(Object, boolean)}, you may wish to override
* {@link #headSet(Object)} to forward to this implementation.
*/
protected SortedSet<E> standardHeadSet(E toElement) {
return headSet(toElement, false);
}
@Override
public NavigableSet<E> tailSet(E fromElement, boolean inclusive) {
return delegate().tailSet(fromElement, inclusive);
}
/**
* A sensible definition of {@link #tailSet(Object)} in terms of the {@link #tailSet(Object,
* boolean)} method. If you override {@link #tailSet(Object, boolean)}, you may wish to override
* {@link #tailSet(Object)} to forward to this implementation.
*/
protected SortedSet<E> standardTailSet(E fromElement) {
return tailSet(fromElement, true);
}
}