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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.SortedMap;
import javax.annotation.Nullable;
/**
* 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 <a
* href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
*
* <p><i>Warning:</i> The methods of {@code ForwardingSortedMap} forward
* <i>indiscriminately</i> to the methods of the delegate. For example,
* overriding {@link #put} alone <i>will not</i> 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.
*
* <p>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}.
*
* <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 ForwardingSortedMap<K, V> extends ForwardingMap<K, V>
implements SortedMap<K, V> {
// TODO(user): identify places where thread safety is actually lost
/** Constructor for use by subclasses. */
protected ForwardingSortedMap() {}
@Override protected abstract SortedMap<K, V> delegate();
@Override
public Comparator<? super K> comparator() {
return delegate().comparator();
}
@Override
public K firstKey() {
return delegate().firstKey();
}
@Override
public SortedMap<K, V> headMap(K toKey) {
return delegate().headMap(toKey);
}
@Override
public K lastKey() {
return delegate().lastKey();
}
@Override
public SortedMap<K, V> subMap(K fromKey, K toKey) {
return delegate().subMap(fromKey, toKey);
}
@Override
public SortedMap<K, V> tailMap(K fromKey) {
return delegate().tailMap(fromKey);
}
// unsafe, but worst case is a CCE is thrown, which callers will be expecting
@SuppressWarnings("unchecked")
private int unsafeCompare(Object k1, Object k2) {
Comparator<? super K> comparator = comparator();
if (comparator == null) {
return ((Comparable<Object>) k1).compareTo(k2);
} else {
return ((Comparator<Object>) 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(@Nullable Object key) {
try {
// any CCE will be caught
@SuppressWarnings("unchecked")
SortedMap<Object, V> self = (SortedMap<Object, V>) this;
Object ceilingKey = self.tailMap(key).firstKey();
return unsafeCompare(ceilingKey, key) == 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()} of the {@code entrySet()} of {@link #tailMap}. If you override
* {@link #tailMap}, you may wish to override {@link #remove} to forward
* to this implementation.
*
* @since 7.0
*/
@Override @Beta protected V standardRemove(@Nullable Object key) {
try {
// any CCE will be caught
@SuppressWarnings("unchecked")
SortedMap<Object, V> self = (SortedMap<Object, V>) this;
Iterator<Entry<Object, V>> entryIterator =
self.tailMap(key).entrySet().iterator();
if (entryIterator.hasNext()) {
Entry<Object, V> ceilingEntry = entryIterator.next();
if (unsafeCompare(ceilingEntry.getKey(), key) == 0) {
V value = ceilingEntry.getValue();
entryIterator.remove();
return value;
}
}
} catch (ClassCastException e) {
return null;
} catch (NullPointerException e) {
return null;
}
return null;
}
/**
* 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<K, V> standardSubMap(K fromKey, K toKey) {
return tailMap(fromKey).headMap(toKey);
}
}
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