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// Copyright 2014 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.xcode.util;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.collect.Multimap;
import java.util.Collection;
import java.util.Map;
/**
* Provides methods that make checking for the presence of an item in a collection type-safe. For
* instance, in {@code foo.containsKey(bar)}, where {@code foo} is a {@code Map<K, V>}, {@code bar}
* can be a type other than {@code K} and may be {@code null}, in which case the method will just
* return false (collections that allow null references may of course return true in the latter
* case).
* <p>
* The methods in this class, such as {@link #key(Map, Object)}, will cause a compiler error if you
* use the wrong type and throw a {@link NullPointerException} if you pass {@code null} for the
* object whose presence to check. In the case where you want to check for {@code null} in a
* collection, add a new method to this class, use the methods in the plain Collections API
* (such as {@link Collection#contains(Object)}), or use the {@code Optional} type as the element of
* the collection.
* <p>
* TODO(bazel-team): This class should either be simplified or eliminated when the
* CollectionIncompatibleType feature is available:
* https://code.google.com/p/error-prone/wiki/CollectionIncompatibleType
*/
public class Containing {
private Containing() {
throw new UnsupportedOperationException("static-only");
}
public static <K> boolean key(Map<K, ?> map, K key) {
checkNotNull(key);
return map.containsKey(key);
}
public static <K> boolean key(Multimap<K, ?> map, K key) {
checkNotNull(key);
return map.containsKey(key);
}
public static <E> boolean item(Collection<E> collection, E item) {
checkNotNull(item);
return collection.contains(item);
}
public static <V> boolean value(Map<?, V> map, V value) {
checkNotNull(value);
return map.containsValue(value);
}
public static <V> boolean value(Multimap<?, V> map, V value) {
checkNotNull(value);
return map.containsValue(value);
}
}
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