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diff --git a/src/main/java/org/apache/commons/math/stat/descriptive/AbstractUnivariateStatistic.java b/src/main/java/org/apache/commons/math/stat/descriptive/AbstractUnivariateStatistic.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.math.stat.descriptive;
+
+import org.apache.commons.math.MathRuntimeException;
+import org.apache.commons.math.exception.DimensionMismatchException;
+import org.apache.commons.math.exception.NotPositiveException;
+import org.apache.commons.math.exception.NullArgumentException;
+import org.apache.commons.math.exception.util.LocalizedFormats;
+
+/**
+ * Abstract base class for all implementations of the
+ * {@link UnivariateStatistic} interface.
+ * <p>
+ * Provides a default implementation of <code>evaluate(double[]),</code>
+ * delegating to <code>evaluate(double[], int, int)</code> in the natural way.
+ * </p>
+ * <p>
+ * Also includes a <code>test</code> method that performs generic parameter
+ * validation for the <code>evaluate</code> methods.</p>
+ *
+ * @version $Revision: 1006299 $ $Date: 2010-10-10 16:47:17 +0200 (dim. 10 oct. 2010) $
+ */
+public abstract class AbstractUnivariateStatistic
+    implements UnivariateStatistic {
+
+    /** Stored data. */
+    private double[] storedData;
+
+    /**
+     * Set the data array.
+     * <p>
+     * The stored value is a copy of the parameter array, not the array itself
+     * </p>
+     * @param values data array to store (may be null to remove stored data)
+     * @see #evaluate()
+     */
+    public void setData(final double[] values) {
+        storedData = (values == null) ? null : values.clone();
+    }
+
+    /**
+     * Get a copy of the stored data array.
+     * @return copy of the stored data array (may be null)
+     */
+    public double[] getData() {
+        return (storedData == null) ? null : storedData.clone();
+    }
+
+    /**
+     * Get a reference to the stored data array.
+     * @return reference to the stored data array (may be null)
+     */
+    protected double[] getDataRef() {
+        return storedData;
+    }
+
+    /**
+     * Set the data array.
+     * @param values data array to store
+     * @param begin the index of the first element to include
+     * @param length the number of elements to include
+     * @see #evaluate()
+     */
+    public void setData(final double[] values, final int begin, final int length) {
+        storedData = new double[length];
+        System.arraycopy(values, begin, storedData, 0, length);
+    }
+
+    /**
+     * Returns the result of evaluating the statistic over the stored data.
+     * <p>
+     * The stored array is the one which was set by previous calls to
+     * </p>
+     * @return the value of the statistic applied to the stored data
+     */
+    public double evaluate() {
+        return evaluate(storedData);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public double evaluate(final double[] values) {
+        test(values, 0, 0);
+        return evaluate(values, 0, values.length);
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    public abstract double evaluate(final double[] values, final int begin, final int length);
+
+    /**
+     * {@inheritDoc}
+     */
+    public abstract UnivariateStatistic copy();
+
+    /**
+     * This method is used by <code>evaluate(double[], int, int)</code> methods
+     * to verify that the input parameters designate a subarray of positive length.
+     * <p>
+     * <ul>
+     * <li>returns <code>true</code> iff the parameters designate a subarray of
+     * positive length</li>
+     * <li>throws <code>IllegalArgumentException</code> if the array is null or
+     * or the indices are invalid</li>
+     * <li>returns <code>false</li> if the array is non-null, but
+     * <code>length</code> is 0.
+     * </ul></p>
+     *
+     * @param values the input array
+     * @param begin index of the first array element to include
+     * @param length the number of elements to include
+     * @return true if the parameters are valid and designate a subarray of positive length
+     * @throws IllegalArgumentException if the indices are invalid or the array is null
+     */
+    protected boolean test(
+        final double[] values,
+        final int begin,
+        final int length) {
+
+        if (values == null) {
+            throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY);
+        }
+
+        if (begin < 0) {
+            throw new NotPositiveException(LocalizedFormats.START_POSITION, begin);
+        }
+
+        if (length < 0) {
+            throw new NotPositiveException(LocalizedFormats.LENGTH, length);
+        }
+
+        if (begin + length > values.length) {
+            throw MathRuntimeException.createIllegalArgumentException(
+                  LocalizedFormats.SUBARRAY_ENDS_AFTER_ARRAY_END);
+        }
+
+        if (length == 0) {
+            return false;
+        }
+
+        return true;
+
+    }
+
+    /**
+     * This method is used by <code>evaluate(double[], double[], int, int)</code> methods
+     * to verify that the begin and length parameters designate a subarray of positive length
+     * and the weights are all non-negative, non-NaN, finite, and not all zero.
+     * <p>
+     * <ul>
+     * <li>returns <code>true</code> iff the parameters designate a subarray of
+     * positive length and the weights array contains legitimate values.</li>
+     * <li>throws <code>IllegalArgumentException</code> if any of the following are true:
+     * <ul><li>the values array is null</li>
+     *     <li>the weights array is null</li>
+     *     <li>the weights array does not have the same length as the values array</li>
+     *     <li>the weights array contains one or more infinite values</li>
+     *     <li>the weights array contains one or more NaN values</li>
+     *     <li>the weights array contains negative values</li>
+     *     <li>the start and length arguments do not determine a valid array</li></ul>
+     * </li>
+     * <li>returns <code>false</li> if the array is non-null, but
+     * <code>length</code> is 0.
+     * </ul></p>
+     *
+     * @param values the input array
+     * @param weights the weights array
+     * @param begin index of the first array element to include
+     * @param length the number of elements to include
+     * @return true if the parameters are valid and designate a subarray of positive length
+     * @throws IllegalArgumentException if the indices are invalid or the array is null
+     * @since 2.1
+     */
+    protected boolean test(
+        final double[] values,
+        final double[] weights,
+        final int begin,
+        final int length) {
+
+        if (weights == null) {
+            throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY);
+        }
+
+        if (weights.length != values.length) {
+            throw new DimensionMismatchException(weights.length, values.length);
+        }
+
+        boolean containsPositiveWeight = false;
+        for (int i = begin; i < begin + length; i++) {
+            if (Double.isNaN(weights[i])) {
+                throw MathRuntimeException.createIllegalArgumentException(
+                        LocalizedFormats.NAN_ELEMENT_AT_INDEX, i);
+            }
+            if (Double.isInfinite(weights[i])) {
+                throw MathRuntimeException.createIllegalArgumentException(
+                        LocalizedFormats.INFINITE_ARRAY_ELEMENT, weights[i], i);
+            }
+            if (weights[i] < 0) {
+                throw MathRuntimeException.createIllegalArgumentException(
+                      LocalizedFormats.NEGATIVE_ELEMENT_AT_INDEX, i, weights[i]);
+            }
+            if (!containsPositiveWeight && weights[i] > 0.0) {
+                containsPositiveWeight = true;
+            }
+        }
+
+        if (!containsPositiveWeight) {
+            throw MathRuntimeException.createIllegalArgumentException(
+                    LocalizedFormats.WEIGHT_AT_LEAST_ONE_NON_ZERO);
+        }
+
+        return test(values, begin, length);
+    }
+}
+