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: 155427 $ $Date: 2005-02-26 06:11:52 -0700 (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 }