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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 static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import java.util.Comparator;
import java.util.NoSuchElementException;
import java.util.SortedMap;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;

/**
 * A sorted map which forwards all its method calls to another sorted map. Subclasses should
 * override one or more methods to modify the behavior of the backing sorted map as desired per the
 * decorator pattern.
 *
 * 

Warning: The methods of {@code ForwardingSortedMap} forward indiscriminately to * the methods of the delegate. For example, overriding {@link #put} alone will not change * the behavior of {@link #putAll}, which can lead to unexpected behavior. In this case, you should * override {@code putAll} as well, either providing your own implementation, or delegating to the * provided {@code standardPutAll} 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 ForwardingSortedMap}. * *

Each of the {@code standard} methods, where appropriate, use the comparator of the map to test * equality for both keys and values, unlike {@code ForwardingMap}. * *

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 ForwardingSortedMap extends ForwardingMap implements SortedMap { // TODO(lowasser): identify places where thread safety is actually lost /** Constructor for use by subclasses. */ protected ForwardingSortedMap() {} @Override protected abstract SortedMap delegate(); @Override public Comparator comparator() { return delegate().comparator(); } @Override public K firstKey() { return delegate().firstKey(); } @Override public SortedMap headMap(K toKey) { return delegate().headMap(toKey); } @Override public K lastKey() { return delegate().lastKey(); } @Override public SortedMap subMap(K fromKey, K toKey) { return delegate().subMap(fromKey, toKey); } @Override public SortedMap tailMap(K fromKey) { return delegate().tailMap(fromKey); } /** * A sensible implementation of {@link SortedMap#keySet} in terms of the methods of {@code * ForwardingSortedMap}. In many cases, you may wish to override {@link * ForwardingSortedMap#keySet} to forward to this implementation or a subclass thereof. * * @since 15.0 */ @Beta protected class StandardKeySet extends Maps.SortedKeySet { /** Constructor for use by subclasses. */ public StandardKeySet() { super(ForwardingSortedMap.this); } } // unsafe, but worst case is a CCE is thrown, which callers will be expecting @SuppressWarnings("unchecked") private int unsafeCompare(Object k1, Object k2) { Comparator comparator = comparator(); if (comparator == null) { return ((Comparable) k1).compareTo(k2); } else { return ((Comparator) comparator).compare(k1, k2); } } /** * A sensible definition of {@link #containsKey} in terms of the {@code firstKey()} method of * {@link #tailMap}. If you override {@link #tailMap}, you may wish to override {@link * #containsKey} to forward to this implementation. * * @since 7.0 */ @Override @Beta protected boolean standardContainsKey(@NullableDecl Object key) { try { // any CCE will be caught @SuppressWarnings("unchecked") SortedMap self = (SortedMap) this; Object ceilingKey = self.tailMap(key).firstKey(); return unsafeCompare(ceilingKey, key) == 0; } catch (ClassCastException | NoSuchElementException | NullPointerException e) { return false; } } /** * A sensible default implementation of {@link #subMap(Object, Object)} in terms of {@link * #headMap(Object)} and {@link #tailMap(Object)}. In some situations, you may wish to override * {@link #subMap(Object, Object)} to forward to this implementation. * * @since 7.0 */ @Beta protected SortedMap standardSubMap(K fromKey, K toKey) { checkArgument(unsafeCompare(fromKey, toKey) <= 0, "fromKey must be <= toKey"); return tailMap(fromKey).headMap(toKey); } }