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Swirlds is a software platform designed to build fully-distributed applications that harness the power of the cloud without servers. Now you can develop applications with fairness in decision making, speed, trust and reliability, at a fraction of the cost of traditional server-based platforms.

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/*
 * Copyright (C) 2018-2024 Hedera Hashgraph, LLC
 *
 * 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.swirlds.common.merkle.utility;

/**
 * 
 * Describes an object that contains a key.
 * 
 *
 * 
 * If a Keyed object implements {@link com.swirlds.common.FastCopyable FastCopyable}, a
 * {@link com.swirlds.common.FastCopyable#copy() copy()} operation is expected to copy the key.
 * 
 *
 * 
 * If a Keyed object implements {@link com.swirlds.common.crypto.Hashable Hashable}
 * then the key is expected to be hashed.
 * 
 *
 * 
 * If a Keyed object is capable of being serialized and deserialized
 * then the key is expected to be serialized and deserialized as well.
 * 
 *
 * @param 
 * 		the type of the key, each instance of this type must be effectively immutable
 * 		(that is, no operation after initial construction should be capable of changing the
 * 		behavior of {@link Object#hashCode()} or {@link Object#equals(Object)}.
 */
public interface Keyed {

    /**
     * Get the key that corresponds to this object. Must always return the last object supplied by
     * {@link #setKey(Object)}, or null if {@link #setKey(Object)} has never been called.
     *
     * @return the key that corresponds to this object
     */
    K getKey();

    /**
     * Set the key that corresponds to this object.
     *
     * @param key
     * 		the new key for this object
     */
    void setKey(K key);
}