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    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: 1.13 $ $Date: 2004/06/23 16:26:16 $
    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 }