001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.math3.util;
018
019
020/**
021 * Provides a standard interface for double arrays.  Allows different
022 * array implementations to support various storage mechanisms
023 * such as automatic expansion, contraction, and array "rolling".
024 *
025 * @version $Id: DoubleArray.java 1416643 2012-12-03 19:37:14Z tn $
026 */
027public interface DoubleArray {
028
029    /**
030     * Returns the number of elements currently in the array.  Please note
031     * that this may be different from the length of the internal storage array.
032     *
033     * @return number of elements
034     */
035    int getNumElements();
036
037    /**
038     * Returns the element at the specified index.  Note that if an
039     * out of bounds index is supplied a ArrayIndexOutOfBoundsException
040     * will be thrown.
041     *
042     * @param index index to fetch a value from
043     * @return value stored at the specified index
044     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
045     *         zero or is greater than <code>getNumElements() - 1</code>.
046     */
047    double getElement(int index);
048
049    /**
050     * Sets the element at the specified index.  If the specified index is greater than
051     * <code>getNumElements() - 1</code>, the <code>numElements</code> property
052     * is increased to <code>index +1</code> and additional storage is allocated
053     * (if necessary) for the new element and all  (uninitialized) elements
054     * between the new element and the previous end of the array).
055     *
056     * @param index index to store a value in
057     * @param value value to store at the specified index
058     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
059     *         zero.
060     */
061    void setElement(int index, double value);
062
063    /**
064     * Adds an element to the end of this expandable array
065     *
066     * @param value to be added to end of array
067     */
068    void addElement(double value);
069
070    /**
071     * Adds elements to the end of this expandable array
072     *
073     * @param values to be added to end of array
074     */
075    void addElements(double[] values);
076
077    /**
078     * <p>
079     * Adds an element to the end of the array and removes the first
080     * element in the array.  Returns the discarded first element.
081     * The effect is similar to a push operation in a FIFO queue.
082     * </p>
083     * <p>
084     * Example: If the array contains the elements 1, 2, 3, 4 (in that order)
085     * and addElementRolling(5) is invoked, the result is an array containing
086     * the entries 2, 3, 4, 5 and the value returned is 1.
087     * </p>
088     *
089     * @param value the value to be added to the array
090     * @return the value which has been discarded or "pushed" out of the array
091     *         by this rolling insert
092     */
093    double addElementRolling(double value);
094
095    /**
096     * Returns a double[] array containing the elements of this
097     * <code>DoubleArray</code>.  If the underlying implementation is
098     * array-based, this method should always return a copy, rather than a
099     * reference to the underlying array so that changes made to the returned
100     *  array have no effect on the <code>DoubleArray.</code>
101     *
102     * @return all elements added to the array
103     */
104    double[] getElements();
105
106    /**
107     * Clear the double array
108     */
109    void clear();
110
111}