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Collection Query Engine: NoSQL indexing and query engine for Java collections with ultra-low latency
/**
* Copyright 2012-2015 Niall Gallagher
*
* 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.googlecode.cqengine.entity;
import com.googlecode.cqengine.query.QueryFactory;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
/**
* Wrapper for Map to allow efficient use in an IndexCollection.
* MapEntities can be created via {@link QueryFactory#mapEntity(Map)}. Attributes can be created to read the entries
* in these maps, using {@link QueryFactory#mapAttribute(Object, Class)}.
*
* This works by optimizing the performance of the {@link #hashCode()} and {@link #equals(Object)} methods - which
* may be called frequently during query processing. The hashCode of the wrapped Map will be cached to improve the
* performance of repeated invocations of {@link #hashCode()}. The cached hashCode will be used in the
* implementation of the {@link #equals(Object)} method too, to avoid computing equality entirely when the cached
* hashCodes are different.
*
* Note it is not safe to modify entries in maps which are indexed, although non-indexed entries may be modified
* safely. Alternatively, remove and re-add the Map to the collection.
*/
@SuppressWarnings({"unchecked", "NullableProblems"})
public class MapEntity implements Map {
final Map wrappedMap;
final int cachedHashCode;
public MapEntity(Map mapToWrap) {
this(mapToWrap, mapToWrap.hashCode());
}
protected MapEntity(Map mapToWrap, int hashCode) {
wrappedMap = mapToWrap;
cachedHashCode = hashCode;
}
/**
* Returns the wrapped map.
*/
public Map getWrappedMap() {
return wrappedMap;
}
/**
* Returns the hashcode of the wrapped map which was cached when this MapEntity was created.
* @return the hashcode of the wrapped map which was cached when this MapEntity was created.
*/
@Override
public int hashCode() {
return cachedHashCode;
}
/**
* Returns true if the cached hashcodes of both objects are equal and the wrapped maps are equal.
*/
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof MapEntity)) {
return false;
}
MapEntity that = (MapEntity) o;
if (cachedHashCode != that.cachedHashCode) {
return false;
}
return this.wrappedMap.equals(that.wrappedMap);
}
@Override
public String toString() {
return "MapEntity{" +
"cachedHashCode=" + cachedHashCode +
", wrappedMap=" + wrappedMap +
'}';
}
public Object get(Object key) {
return wrappedMap.get(key);
}
@Override
public Object put(Object o, Object o2) {
return wrappedMap.put(o, o2);
}
@Override
public Object remove(Object o) {
return wrappedMap.remove(o);
}
@Override
public void putAll(Map map) {
wrappedMap.putAll(map);
}
@Override
public void clear() {
wrappedMap.clear();
}
@Override
public Set keySet() {
return wrappedMap.keySet();
}
@Override
public Collection values() {
return wrappedMap.values();
}
@Override
public Set entrySet() {
return wrappedMap.entrySet();
}
@Override
public int size() {
return wrappedMap.size();
}
@Override
public boolean isEmpty() {
return wrappedMap.isEmpty();
}
@Override
public boolean containsKey(Object o) {
return wrappedMap.containsKey(o);
}
@Override
public boolean containsValue(Object o) {
return wrappedMap.containsValue(o);
}
}