View Javadoc

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   */
17  package 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: 670469 $ $Date: 2008-06-23 04:01:38 -0400 (Mon, 23 Jun 2008) $
26   */
27  public 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 }