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This artifact provides efficient implementations for various collection data structures (esp. linked lists and priority queues), which have very insufficient implementation in the Java Collections Framework that makes it hard or even impossible to exploit their efficiencies.

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/* Copyright (C) 2013-2018 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 *
 * 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 net.automatalib.commons.smartcollections;

import java.util.Collection;
import java.util.Comparator;

/**
 * A generalized priority queue which allows storing arbitrary elements that don't have to be comparable, neither by
 * their natural ordering nor by a provided {@link Comparator}. Instead, keys can be assigned to the elements
 * explicitly.
 * 
 * Since this interface extends the {@link SmartCollection} (and thus also the {@link Collection}) interface, it has to
 * provide the {@link SmartCollection#referencedAdd(Object)} and {@link Collection#add(Object)} methods with no
 * additional key parameters. This is handled by using a default key, which is implicitly used for all elements
 * inserted using the above methods. Initially, the default key is null, whereas the null key
 * is by convention larger than any non-null key. The default key for consequent insertions can be changed
 * by calling {@link #setDefaultKey(Comparable)}.
 *
 * @param 
 *         element class.
 * @param 
 *         key class.
 *
 * @author Malte Isberner
 */
public interface SmartGeneralPriorityQueue> extends SmartPriorityQueue {

    /**
     * Inserts an element with the specified key.
     *
     * @param elem
     *         the element to insert.
     * @param key
     *         the key for this element.
     *
     * @return the reference to the inserted element.
     */
    ElementReference add(E elem, K key);

    /**
     * Sets the default key, which is used for elements that are inserted with no explicit key specified.
     *
     * @param defaultKey
     *         the new defualt key.
     */
    void setDefaultKey(K defaultKey);

    /**
     * Changes the key of an element in the priority key.
     *
     * @param ref
     *         reference to the element whose key is to be changed.
     * @param newKey
     *         the new key of this element.
     */
    void changeKey(ElementReference ref, K newKey);
}