/*
* 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 com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.SortedSet;
import javax.annotation.Nullable;
/**
* A sorted set which forwards all its method calls to another sorted set.
* Subclasses should override one or more methods to modify the behavior of the
* backing sorted set as desired per the <a
* href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
*
* <p><i>Warning:</i> The methods of {@code ForwardingSortedSet} 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>Each of the {@code standard} methods, where appropriate, 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 Mike Bostock
* @author Louis Wasserman
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible
public abstract class ForwardingSortedSet<E> extends ForwardingSet<E>
implements SortedSet<E> {
/** Constructor for use by subclasses. */
protected ForwardingSortedSet() {}
@Override protected abstract SortedSet<E> delegate();
@Override
public Comparator<? super E> comparator() {
return delegate().comparator();
}
@Override
public E first() {
return delegate().first();
}
@Override
public SortedSet<E> headSet(E toElement) {
return delegate().headSet(toElement);
}
@Override
public E last() {
return delegate().last();
}
@Override
public SortedSet<E> subSet(E fromElement, E toElement) {
return delegate().subSet(fromElement, toElement);
}
@Override
public SortedSet<E> tailSet(E fromElement) {
return delegate().tailSet(fromElement);
}
// unsafe, but worst case is a CCE is thrown, which callers will be expecting
@SuppressWarnings("unchecked")
private int unsafeCompare(Object o1, Object o2) {
Comparator<? super E> comparator = comparator();
return (comparator == null)
? ((Comparable<Object>) o1).compareTo(o2)
: ((Comparator<Object>) comparator).compare(o1, o2);
}
/**
* A sensible definition of {@link #contains} in terms of the {@code first()}
* method of {@link #tailSet}. If you override {@link #tailSet}, you may wish
* to override {@link #contains} to forward to this implementation.
*
* @since 7.0
*/
@Override @Beta protected boolean standardContains(@Nullable Object object) {
try {
// any ClassCastExceptions are caught
@SuppressWarnings("unchecked")
SortedSet<Object> self = (SortedSet<Object>) this;
Object ceiling = self.tailSet(object).first();
return unsafeCompare(ceiling, object) == 0;
} catch (ClassCastException e) {
return false;
} catch (NoSuchElementException e) {
return false;
} catch (NullPointerException e) {
return false;
}
}
/**
* A sensible definition of {@link #remove} in terms of the {@code iterator()}
* method of {@link #tailSet}. If you override {@link #tailSet}, you may wish
* to override {@link #remove} to forward to this implementation.
*
* @since 7.0
*/
@Override @Beta protected boolean standardRemove(@Nullable Object object) {
try {
// any ClassCastExceptions are caught
@SuppressWarnings("unchecked")
SortedSet<Object> self = (SortedSet<Object>) this;
Iterator<Object> iterator = self.tailSet(object).iterator();
if (iterator.hasNext()) {
Object ceiling = iterator.next();
if (unsafeCompare(ceiling, object) == 0) {
iterator.remove();
return true;
}
}
} catch (ClassCastException e) {
return false;
} catch (NullPointerException e) {
return false;
}
return false;
}
/**
* A sensible default implementation of {@link #subSet(Object, Object)} in
* terms of {@link #headSet(Object)} and {@link #tailSet(Object)}. In some
* situations, you may wish to override {@link #subSet(Object, Object)} to
* forward to this implementation.
*
* @since 7.0
*/
@Beta protected SortedSet<E> standardSubSet(E fromElement, E toElement) {
return tailSet(fromElement).headSet(toElement);
}
}
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