com.google.common.collect.ForwardingSortedMap Maven / Gradle / Ivy
/*
* 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.GwtCompatible;
import java.util.Comparator;
import java.util.NoSuchElementException;
import java.util.SortedMap;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.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
* 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
@ElementTypesAreNonnullByDefault
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
@CheckForNull
public Comparator comparator() {
return delegate().comparator();
}
@Override
@ParametricNullness
public K firstKey() {
return delegate().firstKey();
}
@Override
public SortedMap headMap(@ParametricNullness K toKey) {
return delegate().headMap(toKey);
}
@Override
@ParametricNullness
public K lastKey() {
return delegate().lastKey();
}
@Override
public SortedMap subMap(@ParametricNullness K fromKey, @ParametricNullness K toKey) {
return delegate().subMap(fromKey, toKey);
}
@Override
public SortedMap tailMap(@ParametricNullness 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
*/
protected class StandardKeySet extends Maps.SortedKeySet {
/** Constructor for use by subclasses. */
public StandardKeySet() {
super(ForwardingSortedMap.this);
}
}
// unsafe, but worst case is a CCE or NPE is thrown, which callers will be expecting
@SuppressWarnings({"unchecked", "nullness"})
static int unsafeCompare(
@CheckForNull Comparator comparator, @CheckForNull Object o1, @CheckForNull Object o2) {
if (comparator == null) {
return ((Comparable< Object>) o1).compareTo(o2);
} else {
return ((Comparator< Object>) comparator).compare(o1, o2);
}
}
/**
* 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
protected boolean standardContainsKey(@CheckForNull Object key) {
try {
// any CCE or NPE will be caught
@SuppressWarnings({"unchecked", "nullness"})
SortedMap< Object, V> self = (SortedMap< Object, V>) this;
Object ceilingKey = self.tailMap(key).firstKey();
return unsafeCompare(comparator(), 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
*/
protected SortedMap standardSubMap(K fromKey, K toKey) {
checkArgument(unsafeCompare(comparator(), fromKey, toKey) <= 0, "fromKey must be <= toKey");
return tailMap(fromKey).headMap(toKey);
}
}