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Java > Open Source Codes > org > apache > commons > math > util > DoubleArray


1 /*
2  * Copyright 2003-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.math.util;
17
18
19 /**
20  * Provides a standard interface for double arrays. Allows different
21  * array implementations to support various storage mechanisms
22  * such as automatic expansion, contraction, and array "rolling".
23  *
24  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
25  */
26 public interface DoubleArray {
27
28     /**
29      * Returns the number of elements currently in the array. Please note
30      * that this may be different from the length of the internal storage array.
31      *
32      * @return number of elements
33      */
34     int getNumElements();
35
36     /**
37      * Returns the element at the specified index. Note that if an
38      * out of bounds index is supplied a ArrayIndexOutOfBoundsException
39      * will be thrown.
40      *
41      * @param index index to fetch a value from
42      * @return value stored at the specified index
43      * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
44      * zero or is greater than <code>getNumElements() - 1</code>.
45      */
46     double getElement(int index);
47
48     /**
49      * Sets the element at the specified index. If the specified index is greater than
50      * <code>getNumElements() - 1</code>, the <code>numElements</code> property
51      * is increased to <code>index +1</code> and additional storage is allocated
52      * (if necessary) for the new element and all (uninitialized) elements
53      * between the new element and the previous end of the array).
54      *
55      * @param index index to store a value in
56      * @param value value to store at the specified index
57      * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than
58      * zero.
59      */
60     void setElement(int index, double value);
61
62     /**
63      * Adds an element to the end of this expandable array
64      *
65      * @param value to be added to end of array
66      */
67     void addElement(double value);
68
69     /**
70      * <p>
71      * Adds an element to the end of the array and removes the first
72      * element in the array. Returns the discarded first element.
73      * The effect is similar to a push operation in a FIFO queue.
74      * </p>
75      * <p>
76      * Example: If the array contains the elements 1, 2, 3, 4 (in that order)
77      * and addElementRolling(5) is invoked, the result is an array containing
78      * the entries 2, 3, 4, 5 and the value returned is 1.
79      * </p>
80      *
81      * @param value the value to be added to the array
82      * @return the value which has been discarded or "pushed" out of the array
83      * by this rolling insert
84      */
85     double addElementRolling(double value);
86
87     /**
88      * Returns a double[] array containing the elements of this
89      * <code>DoubleArray</code>. If the underlying implementation is
90      * array-based, this method should always return a copy, rather than a
91      * reference to the underlying array so that changes made to the returned
92      * array have no effect on the <code>DoubleArray.</code>
93      *
94      * @return all elements added to the array
95      */
96     double[] getElements();
97
98     /**
99      * Clear the double array
100      */
101     void clear();
102
103 }
104
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