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    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;
    19
    20  import org.apache.commons.math.MathException;
    21
    22  /***
    23   * Base class for probability distributions.
    24   *
    25   * @version $Revision: 1.2 $ $Date: 2004/11/07 20:39:15 $
    26   */
    27  public abstract class AbstractDistribution
    28      implements Distribution, Serializable {
    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 &le; X &le; 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
    61              ("lower endpoint must be less than or equal to upper endpoint");
    62          }
    63          return cumulativeProbability(x1) - cumulativeProbability(x0);
    64      }
    65  }