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diff --git a/src/main/java/org/apache/commons/math/distribution/AbstractDistribution.java b/src/main/java/org/apache/commons/math/distribution/AbstractDistribution.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.distribution;
+
+import java.io.Serializable;
+
+import org.apache.commons.math.MathException;
+import org.apache.commons.math.MathRuntimeException;
+import org.apache.commons.math.exception.util.LocalizedFormats;
+
+/**
+ * Base class for probability distributions.
+ *
+ * @version $Revision: 1054524 $ $Date: 2011-01-03 05:59:18 +0100 (lun. 03 janv. 2011) $
+ */
+public abstract class AbstractDistribution
+    implements Distribution, Serializable {
+
+    /** Serializable version identifier */
+    private static final long serialVersionUID = -38038050983108802L;
+
+    /**
+     * Default constructor.
+     */
+    protected AbstractDistribution() {
+        super();
+    }
+
+    /**
+     * For a random variable X whose values are distributed according
+     * to this distribution, this method returns P(x0 &le; X &le; x1).
+     * <p>
+     * The default implementation uses the identity</p>
+     * <p>
+     * P(x0 &le; X &le; x1) = P(X &le; x1) - P(X &le; x0) </p>
+     *
+     * @param x0 the (inclusive) lower bound
+     * @param x1 the (inclusive) upper bound
+     * @return the probability that a random variable with this distribution
+     * will take a value between <code>x0</code> and <code>x1</code>,
+     * including the endpoints.
+     * @throws MathException if the cumulative probability can not be
+     * computed due to convergence or other numerical errors.
+     * @throws IllegalArgumentException if <code>x0 > x1</code>
+     */
+    public double cumulativeProbability(double x0, double x1)
+        throws MathException {
+        if (x0 > x1) {
+            throw MathRuntimeException.createIllegalArgumentException(
+                  LocalizedFormats.LOWER_ENDPOINT_ABOVE_UPPER_ENDPOINT,
+                  x0, x1);
+        }
+        return cumulativeProbability(x1) - cumulativeProbability(x0);
+    }
+}