1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements.  See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License.  You may obtain a copy of the License at
8 *
9 *      http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17package org.apache.commons.math.util;
18
19
20/**
21 * Provides a standard interface for double arrays.  Allows different
22 * array implementations to support various storage mechanisms
23 * such as automatic expansion, contraction, and array "rolling".
24 *
25 * @version $Revision: 811685 $ $Date: 2009-09-05 19:36:48 +0200 (sam. 05 sept. 2009) $
26 */
27public interface DoubleArray {
28
29    /**
30     * Returns the number of elements currently in the array.  Please note
31     * that this may be different from the length of the internal storage array.
32     *
33     * @return number of elements
34     */
35    int getNumElements();
36
37    /**
38     * Returns the element at the specified index.  Note that if an
39     * out of bounds index is supplied a ArrayIndexOutOfBoundsException
40     * will be thrown.
41     *
42     * @param index index to fetch a value from
43     * @return value stored at the specified index
44     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
45     *         zero or is greater than <code>getNumElements() - 1</code>.
46     */
47    double getElement(int index);
48
49    /**
50     * Sets the element at the specified index.  If the specified index is greater than
51     * <code>getNumElements() - 1</code>, the <code>numElements</code> property
52     * is increased to <code>index +1</code> and additional storage is allocated
53     * (if necessary) for the new element and all  (uninitialized) elements
54     * between the new element and the previous end of the array).
55     *
56     * @param index index to store a value in
57     * @param value value to store at the specified index
58     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
59     *         zero.
60     */
61    void setElement(int index, double value);
62
63    /**
64     * Adds an element to the end of this expandable array
65     *
66     * @param value to be added to end of array
67     */
68    void addElement(double value);
69
70    /**
71     * <p>
72     * Adds an element to the end of the array and removes the first
73     * element in the array.  Returns the discarded first element.
74     * The effect is similar to a push operation in a FIFO queue.
75     * </p>
76     * <p>
77     * Example: If the array contains the elements 1, 2, 3, 4 (in that order)
78     * and addElementRolling(5) is invoked, the result is an array containing
79     * the entries 2, 3, 4, 5 and the value returned is 1.
80     * </p>
81     *
82     * @param value the value to be added to the array
83     * @return the value which has been discarded or "pushed" out of the array
84     *         by this rolling insert
85     */
86    double addElementRolling(double value);
87
88    /**
89     * Returns a double[] array containing the elements of this
90     * <code>DoubleArray</code>.  If the underlying implementation is
91     * array-based, this method should always return a copy, rather than a
92     * reference to the underlying array so that changes made to the returned
93     *  array have no effect on the <code>DoubleArray.</code>
94     *
95     * @return all elements added to the array
96     */
97    double[] getElements();
98
99    /**
100     * Clear the double array
101     */
102    void clear();
103
104}
105