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diff --git a/src/main/java/org/apache/commons/math3/util/DoubleArray.java b/src/main/java/org/apache/commons/math3/util/DoubleArray.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.commons.math3.util;
+
+/**
+ * Provides a standard interface for double arrays. Allows different array implementations to
+ * support various storage mechanisms such as automatic expansion, contraction, and array "rolling".
+ */
+public interface DoubleArray {
+
+    /**
+     * Returns the number of elements currently in the array. Please note that this may be different
+     * from the length of the internal storage array.
+     *
+     * @return number of elements
+     */
+    int getNumElements();
+
+    /**
+     * Returns the element at the specified index. Note that if an out of bounds index is supplied a
+     * ArrayIndexOutOfBoundsException will be thrown.
+     *
+     * @param index index to fetch a value from
+     * @return value stored at the specified index
+     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than zero or is greater
+     *     than <code>getNumElements() - 1</code>.
+     */
+    double getElement(int index);
+
+    /**
+     * Sets the element at the specified index. If the specified index is greater than <code>
+     * getNumElements() - 1</code>, the <code>numElements</code> property is increased to <code>
+     * index +1</code> and additional storage is allocated (if necessary) for the new element and
+     * all (uninitialized) elements between the new element and the previous end of the array).
+     *
+     * @param index index to store a value in
+     * @param value value to store at the specified index
+     * @throws ArrayIndexOutOfBoundsException if <code>index</code> is less than zero.
+     */
+    void setElement(int index, double value);
+
+    /**
+     * Adds an element to the end of this expandable array
+     *
+     * @param value to be added to end of array
+     */
+    void addElement(double value);
+
+    /**
+     * Adds elements to the end of this expandable array
+     *
+     * @param values to be added to end of array
+     */
+    void addElements(double[] values);
+
+    /**
+     * Adds an element to the end of the array and removes the first element in the array. Returns
+     * the discarded first element. The effect is similar to a push operation in a FIFO queue.
+     *
+     * <p>Example: If the array contains the elements 1, 2, 3, 4 (in that order) and
+     * addElementRolling(5) is invoked, the result is an array containing the entries 2, 3, 4, 5 and
+     * the value returned is 1.
+     *
+     * @param value the value to be added to the array
+     * @return the value which has been discarded or "pushed" out of the array by this rolling
+     *     insert
+     */
+    double addElementRolling(double value);
+
+    /**
+     * Returns a double[] array containing the elements of this <code>DoubleArray</code>. If the
+     * underlying implementation is array-based, this method should always return a copy, rather
+     * than a reference to the underlying array so that changes made to the returned array have no
+     * effect on the <code>DoubleArray.</code>
+     *
+     * @return all elements added to the array
+     */
+    double[] getElements();
+
+    /** Clear the double array */
+    void clear();
+}