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 */
017 package org.apache.commons.math.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 $Revision: 811685 $ $Date: 2009-09-05 19:36:48 +0200 (sam. 05 sept. 2009) $
026 */
027 public 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 * <p>
072 * Adds an element to the end of the array and removes the first
073 * element in the array. Returns the discarded first element.
074 * The effect is similar to a push operation in a FIFO queue.
075 * </p>
076 * <p>
077 * Example: If the array contains the elements 1, 2, 3, 4 (in that order)
078 * and addElementRolling(5) is invoked, the result is an array containing
079 * the entries 2, 3, 4, 5 and the value returned is 1.
080 * </p>
081 *
082 * @param value the value to be added to the array
083 * @return the value which has been discarded or "pushed" out of the array
084 * by this rolling insert
085 */
086 double addElementRolling(double value);
087
088 /**
089 * Returns a double[] array containing the elements of this
090 * <code>DoubleArray</code>. If the underlying implementation is
091 * array-based, this method should always return a copy, rather than a
092 * reference to the underlying array so that changes made to the returned
093 * array have no effect on the <code>DoubleArray.</code>
094 *
095 * @return all elements added to the array
096 */
097 double[] getElements();
098
099 /**
100 * Clear the double array
101 */
102 void clear();
103
104 }