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Java > Open Source Codes > org > apache > commons > math > stat > descriptive > AbstractUnivariateStatistic


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.stat.descriptive;
17
18 import java.io.Serializable JavaDoc;
19
20 /**
21  * Abstract base class for all implementations of the
22  * {@link UnivariateStatistic} interface.
23  * <p>
24  * Provides a default implementation of <code>evaluate(double[]),</code>
25  * delegating to <code>evaluate(double[], int, int)</code> in the natural way.
26  * <p>
27  * Also includes a <code>test</code> method that performs generic parameter
28  * validation for the <code>evaluate</code> methods.
29  * <p>
30  *
31  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
32  */
33 public abstract class AbstractUnivariateStatistic
34     implements UnivariateStatistic, Serializable JavaDoc {
35     
36     /** Serialization UID */
37     static final long serialVersionUID = -8007759382851708045L;
38
39     /**
40      * @see org.apache.commons.math.stat.descriptive.UnivariateStatistic#evaluate(double[])
41      */
42     public double evaluate(final double[] values) {
43         test(values, 0, 0);
44         return evaluate(values, 0, values.length);
45     }
46
47     /**
48      * @see org.apache.commons.math.stat.descriptive.UnivariateStatistic#evaluate(double[], int, int)
49      */
50     public abstract double evaluate(final double[] values, final int begin, final int length);
51
52     /**
53      * This method is used by <code>evaluate(double[], int, int)</code> methods
54      * to verify that the input parameters designate a subarray of positive length.
55      * <p>
56      * <ul>
57      * <li>returns <code>true</code> iff the parameters designate a subarray of
58      * positive length</li>
59      * <li>throws <code>IllegalArgumentException</code> if the array is null or
60      * or the indices are invalid</li>
61      * <li>returns <code>false</li> if the array is non-null, but
62      * <code>length</code> is 0.
63      * </ul>
64      *
65      * @param values the input array
66      * @param begin index of the first array element to include
67      * @param length the number of elements to include
68      * @return true if the parameters are valid and designate a subarray of positive length
69      * @throws IllegalArgumentException if the indices are invalid or the array is null
70      */
71     protected boolean test(
72         final double[] values,
73         final int begin,
74         final int length) {
75
76         if (values == null) {
77             throw new IllegalArgumentException JavaDoc("input value array is null");
78         }
79         
80         if (begin < 0) {
81             throw new IllegalArgumentException JavaDoc("start position cannot be negative");
82         }
83         
84         if (length < 0) {
85             throw new IllegalArgumentException JavaDoc("length cannot be negative");
86         }
87         
88         if (begin + length > values.length) {
89             throw new IllegalArgumentException JavaDoc(
90                 "begin + length > values.length");
91         }
92
93         if (length == 0) {
94             return false;
95         }
96
97         return true;
98
99     }
100 }
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