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Java > Open Source Codes > org > apache > commons > math > distribution > AbstractDistribution


1 /*
2  * Copyright 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.distribution;
17
18 import java.io.Serializable JavaDoc;
19
20 import org.apache.commons.math.MathException;
21
22 /**
23  * Base class for probability distributions.
24  *
25  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
26  */
27 public abstract class AbstractDistribution
28     implements Distribution, Serializable JavaDoc {
29
30     /** Serializable version identifier */
31     static final long serialVersionUID = -38038050983108802L;
32     
33     /**
34      * Default constructor.
35      */
36     protected AbstractDistribution() {
37         super();
38     }
39
40     /**
41      * For a random variable X whose values are distributed according
42      * to this distribution, this method returns P(x0 ≤ X ≤ x1).
43      * <p>
44      * The default implementation uses the identity
45      * <p>
46      * P(x0 &le; X &le; x1) = P(X &le; x1) - P(X &le; x0)
47      *
48      * @param x0 the (inclusive) lower bound
49      * @param x1 the (inclusive) upper bound
50      * @return the probability that a random variable with this distribution
51      * will take a value between <code>x0</code> and <code>x1</code>,
52      * including the endpoints.
53      * @throws MathException if the cumulative probability can not be
54      * computed due to convergence or other numerical errors.
55      * @throws IllegalArgumentException if <code>x0 > x1</code>
56      */
57     public double cumulativeProbability(double x0, double x1)
58         throws MathException {
59         if (x0 > x1) {
60             throw new IllegalArgumentException JavaDoc
61             ("lower endpoint must be less than or equal to upper endpoint");
62         }
63         return cumulativeProbability(x1) - cumulativeProbability(x0);
64     }
65 }
66
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