geode-core/src/main/java/org/apache/geode/cache/query/internal/HashingStrategy.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to You 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 org.apache.geode.cache.query.internal;

import java.io.Serializable;

/**
 * This interface defines a Hashing strategy for keys(OR values) in a HashMap(OR HashSet) for
 * calculation of hash-code for custom objects and primitive types.
 *
 * @since GemFire 8.0
 *
 */
public interface HashingStrategy extends Serializable {

  /**
   * Computes a hash code for the specified object. Implementors can use the object's own
   * <tt>hashCode</tt> method, the Java runtime's <tt>identityHashCode</tt>, or a custom scheme.
   *
   * @param o object for which the hash-code is to be computed
   * @return the hashCode
   */
  int hashCode(Object o);

  /**
   * Compares o1 and o2 for equality. Strategy implementors may use the objects' own equals()
   * methods, compare object references, or implement some custom scheme.
   *
   * @param o1 an <code>Object</code> value
   * @param o2 an <code>Object</code> value
   * @return true if the objects are equal according to this strategy.
   */
  boolean equals(Object o1, Object o2);
}