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A set of utilities and tools to speed up and ease programming in Java.
There is a newer version: 0.5
/*
 * (c) 2005 David B. Bracewell
 *
 * 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 com.davidbracewell.collection;

import java.util.List;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 * An index represents a mapping from an Item to an id. 
 *
 * @param  the type parameter
 * @author David B. Bracewell
 */
public interface Index extends Iterable {

  /**
   * Adds an item to the index. If the item is already in the index, the item's id is returned.
   *
   * @param item the item to add
   * @return The index of the item
   */
  int add(E item);

  /**
   * Adds all the items in the iterable to the index
   *
   * @param items The items to add.
   */
  void addAll(Iterable items);

  /**
   * Gets the id of the item or -1 if it is not in the index.
   *
   * @param item The item whose id we want
   * @return The id of the item or -1 if it is not in the index
   */
  int indexOf(E item);

  /**
   * Gets the item with the given id.
   *
   * @param id The id
   * @return The item associated with the id or null if there is none.
   */
  E get(int id);

  /**
   * Clears the index
   */
  void clear();

  /**
   * Size int.
   *
   * @return The number of items in the index
   */
  int size();

  /**
   * Is empty.
   *
   * @return True if there are no items in the index
   */
  boolean isEmpty();

  /**
   * Removes the item with the given id from the index
   *
   * @param id The id to remove
   * @return A mapping of old to new ids
   */
  E remove(int id);

  /**
   * Removes the item from the index
   *
   * @param item The item to remove
   * @return A mapping of old to new ids
   */
  int remove(E item);

  /**
   * Determines if an item is in the index
   *
   * @param item The item
   * @return True if the item is in the index, False if not
   */
  boolean contains(E item);

  /**
   * As list.
   *
   * @return The index as an unmodifiable list.
   */
  List asList();

  /**
   * Sets the item at a given index value. Implementations should throw runtime exceptions if the new value is already
   * in the index or the given index (int) is too large for the index.
   *
   * @param index    the index
   * @param newValue the new value
   * @return The old value
   */
  E set(int index, E newValue);

  /**
   * Stream stream.
   *
   * @return the stream
   */
  default Stream stream() {
    return StreamSupport.stream(spliterator(), false);
  }

  /**
   * Parallel stream.
   *
   * @return the stream
   */
  default Stream parallelStream() {
    return StreamSupport.stream(spliterator(), true);
  }

}//END OF Index