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.math4.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 */
026public interface DoubleArray {
027
028    /**
029     * Returns the number of elements currently in the array.  Please note
030     * that this may be different from the length of the internal storage array.
031     *
032     * @return number of elements
033     */
034    int getNumElements();
035
036    /**
037     * Returns the element at the specified index.  Note that if an
038     * out of bounds index is supplied a ArrayIndexOutOfBoundsException
039     * will be thrown.
040     *
041     * @param index index to fetch a value from
042     * @return value stored at the specified index
043     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
044     *         zero or is greater than <code>getNumElements() - 1</code>.
045     */
046    double getElement(int index);
047
048    /**
049     * Sets the element at the specified index.  If the specified index is greater than
050     * <code>getNumElements() - 1</code>, the <code>numElements</code> property
051     * is increased to <code>index +1</code> and additional storage is allocated
052     * (if necessary) for the new element and all  (uninitialized) elements
053     * between the new element and the previous end of the array).
054     *
055     * @param index index to store a value in
056     * @param value value to store at the specified index
057     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
058     *         zero.
059     */
060    void setElement(int index, double value);
061
062    /**
063     * Adds an element to the end of this expandable array
064     *
065     * @param value to be added to end of array
066     */
067    void addElement(double value);
068
069    /**
070     * Adds elements to the end of this expandable array
071     *
072     * @param values to be added to end of array
073     */
074    void addElements(double[] values);
075
076    /**
077     * <p>
078     * Adds an element to the end of the array and removes the first
079     * element in the array.  Returns the discarded first element.
080     * The effect is similar to a push operation in a FIFO queue.
081     * </p>
082     * <p>
083     * Example: If the array contains the elements 1, 2, 3, 4 (in that order)
084     * and addElementRolling(5) is invoked, the result is an array containing
085     * the entries 2, 3, 4, 5 and the value returned is 1.
086     * </p>
087     *
088     * @param value the value to be added to the array
089     * @return the value which has been discarded or "pushed" out of the array
090     *         by this rolling insert
091     */
092    double addElementRolling(double value);
093
094    /**
095     * Returns a double[] array containing the elements of this
096     * <code>DoubleArray</code>.  If the underlying implementation is
097     * array-based, this method should always return a copy, rather than a
098     * reference to the underlying array so that changes made to the returned
099     *  array have no effect on the <code>DoubleArray.</code>
100     *
101     * @return all elements added to the array
102     */
103    double[] getElements();
104
105    /**
106     * Clear the double array
107     */
108    void clear();
109
110}