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/*
 * 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 org.checkerframework.checker.nullness.qual.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
 * decorator pattern.
 *
 * 

Warning: The methods of {@code ForwardingSortedSet} forward indiscriminately to * the methods of the delegate. For example, overriding {@link #add} alone will not 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. * *

{@code default} method warning: This class does not forward calls to {@code * default} methods. Instead, it inherits their default implementations. When those implementations * invoke methods, they invoke methods on the {@code ForwardingSortedSet}. * *

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. * *

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 */ @GwtCompatible public abstract class ForwardingSortedSet extends ForwardingSet implements SortedSet { /** Constructor for use by subclasses. */ protected ForwardingSortedSet() {} @Override protected abstract SortedSet delegate(); @Override public Comparator comparator() { return delegate().comparator(); } @Override public E first() { return delegate().first(); } @Override public SortedSet headSet(E toElement) { return delegate().headSet(toElement); } @Override public E last() { return delegate().last(); } @Override public SortedSet subSet(E fromElement, E toElement) { return delegate().subSet(fromElement, toElement); } @Override public SortedSet 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(@Nullable Object o1, @Nullable Object o2) { Comparator comparator = comparator(); return (comparator == null) ? ((Comparable) o1).compareTo(o2) : ((Comparator) 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 self = (SortedSet) this; Object ceiling = self.tailSet(object).first(); return unsafeCompare(ceiling, object) == 0; } catch (ClassCastException | NoSuchElementException | 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 self = (SortedSet) this; Iterator iterator = self.tailSet(object).iterator(); if (iterator.hasNext()) { Object ceiling = iterator.next(); if (unsafeCompare(ceiling, object) == 0) { iterator.remove(); return true; } } } catch (ClassCastException | 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 standardSubSet(E fromElement, E toElement) { return tailSet(fromElement).headSet(toElement); } }