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diff --git a/src/main/java/org/apache/commons/math/stat/Frequency.java b/src/main/java/org/apache/commons/math/stat/Frequency.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;
+
+import java.io.Serializable;
+import java.text.NumberFormat;
+import java.util.Iterator;
+import java.util.Comparator;
+import java.util.TreeMap;
+
+import org.apache.commons.math.MathRuntimeException;
+import org.apache.commons.math.exception.util.LocalizedFormats;
+
+/**
+ * Maintains a frequency distribution.
+ * <p>
+ * Accepts int, long, char or Comparable values.  New values added must be
+ * comparable to those that have been added, otherwise the add method will
+ * throw an IllegalArgumentException.</p>
+ * <p>
+ * Integer values (int, long, Integer, Long) are not distinguished by type --
+ * i.e. <code>addValue(Long.valueOf(2)), addValue(2), addValue(2l)</code> all have
+ * the same effect (similarly for arguments to <code>getCount,</code> etc.).</p>
+ * <p>
+ * char values are converted by <code>addValue</code> to Character instances.
+ * As such, these values are not comparable to integral values, so attempts
+ * to combine integral types with chars in a frequency distribution will fail.
+ * </p>
+ * <p>
+ * The values are ordered using the default (natural order), unless a
+ * <code>Comparator</code> is supplied in the constructor.</p>
+ *
+ * @version $Revision: 1054186 $ $Date: 2011-01-01 03:28:46 +0100 (sam. 01 janv. 2011) $
+ */
+public class Frequency implements Serializable {
+
+    /** Serializable version identifier */
+    private static final long serialVersionUID = -3845586908418844111L;
+
+    /** underlying collection */
+    private final TreeMap<Comparable<?>, Long> freqTable;
+
+    /**
+     * Default constructor.
+     */
+    public Frequency() {
+        freqTable = new TreeMap<Comparable<?>, Long>();
+    }
+
+    /**
+     * Constructor allowing values Comparator to be specified.
+     *
+     * @param comparator Comparator used to order values
+     */
+    @SuppressWarnings("unchecked") // TODO is the cast OK?
+    public Frequency(Comparator<?> comparator) {
+        freqTable = new TreeMap<Comparable<?>, Long>((Comparator<? super Comparable<?>>) comparator);
+    }
+
+    /**
+     * Return a string representation of this frequency
+     * distribution.
+     *
+     * @return a string representation.
+     */
+    @Override
+    public String toString() {
+        NumberFormat nf = NumberFormat.getPercentInstance();
+        StringBuilder outBuffer = new StringBuilder();
+        outBuffer.append("Value \t Freq. \t Pct. \t Cum Pct. \n");
+        Iterator<Comparable<?>> iter = freqTable.keySet().iterator();
+        while (iter.hasNext()) {
+            Comparable<?> value = iter.next();
+            outBuffer.append(value);
+            outBuffer.append('\t');
+            outBuffer.append(getCount(value));
+            outBuffer.append('\t');
+            outBuffer.append(nf.format(getPct(value)));
+            outBuffer.append('\t');
+            outBuffer.append(nf.format(getCumPct(value)));
+            outBuffer.append('\n');
+        }
+        return outBuffer.toString();
+    }
+
+    /**
+     * Adds 1 to the frequency count for v.
+     * <p>
+     * If other objects have already been added to this Frequency, v must
+     * be comparable to those that have already been added.
+     * </p>
+     *
+     * @param v the value to add.
+     * @throws IllegalArgumentException if <code>v</code> is not Comparable,
+     *         or is not comparable with previous entries
+     * @deprecated use {@link #addValue(Comparable)} instead
+     */
+    @Deprecated
+    public void addValue(Object v) {
+        if (v instanceof Comparable<?>){
+            addValue((Comparable<?>) v);
+        } else {
+            throw MathRuntimeException.createIllegalArgumentException(
+                  LocalizedFormats.CLASS_DOESNT_IMPLEMENT_COMPARABLE,
+                  v.getClass().getName());
+        }
+    }
+
+    /**
+     * Adds 1 to the frequency count for v.
+     * <p>
+     * If other objects have already been added to this Frequency, v must
+     * be comparable to those that have already been added.
+     * </p>
+     *
+     * @param v the value to add.
+     * @throws IllegalArgumentException if <code>v</code> is not comparable with previous entries
+     */
+    public void addValue(Comparable<?> v){
+        Comparable<?> obj = v;
+        if (v instanceof Integer) {
+           obj = Long.valueOf(((Integer) v).longValue());
+        }
+        try {
+            Long count = freqTable.get(obj);
+            if (count == null) {
+                freqTable.put(obj, Long.valueOf(1));
+            } else {
+                freqTable.put(obj, Long.valueOf(count.longValue() + 1));
+            }
+        } catch (ClassCastException ex) {
+            //TreeMap will throw ClassCastException if v is not comparable
+            throw MathRuntimeException.createIllegalArgumentException(
+                  LocalizedFormats.INSTANCES_NOT_COMPARABLE_TO_EXISTING_VALUES,
+                  v.getClass().getName());
+        }
+    }
+
+    /**
+     * Adds 1 to the frequency count for v.
+     *
+     * @param v the value to add.
+     */
+    public void addValue(int v) {
+        addValue(Long.valueOf(v));
+    }
+
+    /**
+     * Adds 1 to the frequency count for v.
+     *
+     * @param v the value to add.
+     * @deprecated to be removed in math 3.0
+     */
+    @Deprecated
+    public void addValue(Integer v) {
+        addValue(Long.valueOf(v.longValue()));
+    }
+
+    /**
+     * Adds 1 to the frequency count for v.
+     *
+     * @param v the value to add.
+     */
+    public void addValue(long v) {
+        addValue(Long.valueOf(v));
+    }
+
+    /**
+     * Adds 1 to the frequency count for v.
+     *
+     * @param v the value to add.
+     */
+    public void addValue(char v) {
+        addValue(Character.valueOf(v));
+    }
+
+    /** Clears the frequency table */
+    public void clear() {
+        freqTable.clear();
+    }
+
+    /**
+     * Returns an Iterator over the set of values that have been added.
+     * <p>
+     * If added values are integral (i.e., integers, longs, Integers, or Longs),
+     * they are converted to Longs when they are added, so the objects returned
+     * by the Iterator will in this case be Longs.</p>
+     *
+     * @return values Iterator
+     */
+    public Iterator<Comparable<?>> valuesIterator() {
+        return freqTable.keySet().iterator();
+    }
+
+    //-------------------------------------------------------------------------
+
+    /**
+     * Returns the sum of all frequencies.
+     *
+     * @return the total frequency count.
+     */
+    public long getSumFreq() {
+        long result = 0;
+        Iterator<Long> iterator = freqTable.values().iterator();
+        while (iterator.hasNext())  {
+            result += iterator.next().longValue();
+        }
+        return result;
+    }
+
+    /**
+     * Returns the number of values = v.
+     * Returns 0 if the value is not comparable.
+     *
+     * @param v the value to lookup.
+     * @return the frequency of v.
+     * @deprecated replaced by {@link #getCount(Comparable)} as of 2.0
+     */
+    @Deprecated
+    public long getCount(Object v) {
+        return getCount((Comparable<?>) v);
+    }
+
+    /**
+     * Returns the number of values = v.
+     * Returns 0 if the value is not comparable.
+     *
+     * @param v the value to lookup.
+     * @return the frequency of v.
+     */
+    public long getCount(Comparable<?> v) {
+        if (v instanceof Integer) {
+            return getCount(((Integer) v).longValue());
+        }
+        long result = 0;
+        try {
+            Long count =  freqTable.get(v);
+            if (count != null) {
+                result = count.longValue();
+            }
+        } catch (ClassCastException ex) {
+            // ignore and return 0 -- ClassCastException will be thrown if value is not comparable
+        }
+        return result;
+    }
+
+    /**
+     * Returns the number of values = v.
+     *
+     * @param v the value to lookup.
+     * @return the frequency of v.
+     */
+    public long getCount(int v) {
+        return getCount(Long.valueOf(v));
+    }
+
+    /**
+     * Returns the number of values = v.
+     *
+     * @param v the value to lookup.
+     * @return the frequency of v.
+     */
+    public long getCount(long v) {
+        return getCount(Long.valueOf(v));
+    }
+
+    /**
+     * Returns the number of values = v.
+     *
+     * @param v the value to lookup.
+     * @return the frequency of v.
+     */
+    public long getCount(char v) {
+        return getCount(Character.valueOf(v));
+    }
+
+    /**
+     * Returns the number of values in the frequency table.
+     *
+     * @return the number of unique values that have been added to the frequency table.
+     * @see #valuesIterator()
+     */
+    public int getUniqueCount(){
+        return freqTable.keySet().size();
+    }
+
+    //-------------------------------------------------------------
+
+    /**
+      * Returns the percentage of values that are equal to v
+     * (as a proportion between 0 and 1).
+     * <p>
+     * Returns <code>Double.NaN</code> if no values have been added.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     * @deprecated replaced by {@link #getPct(Comparable)} as of 2.0
+     */
+    @Deprecated
+    public double getPct(Object v) {
+        return getPct((Comparable<?>) v);
+    }
+
+    /**
+     * Returns the percentage of values that are equal to v
+     * (as a proportion between 0 and 1).
+     * <p>
+     * Returns <code>Double.NaN</code> if no values have been added.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     */
+    public double getPct(Comparable<?> v) {
+        final long sumFreq = getSumFreq();
+        if (sumFreq == 0) {
+            return Double.NaN;
+        }
+        return (double) getCount(v) / (double) sumFreq;
+    }
+
+    /**
+     * Returns the percentage of values that are equal to v
+     * (as a proportion between 0 and 1).
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     */
+    public double getPct(int v) {
+        return getPct(Long.valueOf(v));
+    }
+
+    /**
+     * Returns the percentage of values that are equal to v
+     * (as a proportion between 0 and 1).
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     */
+    public double getPct(long v) {
+        return getPct(Long.valueOf(v));
+    }
+
+    /**
+     * Returns the percentage of values that are equal to v
+     * (as a proportion between 0 and 1).
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     */
+    public double getPct(char v) {
+        return getPct(Character.valueOf(v));
+    }
+
+    //-----------------------------------------------------------------------------------------
+
+    /**
+     * Returns the cumulative frequency of values less than or equal to v.
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup.
+     * @return the proportion of values equal to v
+     * @deprecated replaced by {@link #getCumFreq(Comparable)} as of 2.0
+     */
+    @Deprecated
+    public long getCumFreq(Object v) {
+        return getCumFreq((Comparable<?>) v);
+    }
+
+    /**
+     * Returns the cumulative frequency of values less than or equal to v.
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup.
+     * @return the proportion of values equal to v
+     */
+    public long getCumFreq(Comparable<?> v) {
+        if (getSumFreq() == 0) {
+            return 0;
+        }
+        if (v instanceof Integer) {
+            return getCumFreq(((Integer) v).longValue());
+        }
+        @SuppressWarnings("unchecked") // OK, freqTable is Comparable<?>
+        Comparator<Comparable<?>> c = (Comparator<Comparable<?>>) freqTable.comparator();
+        if (c == null) {
+            c = new NaturalComparator();
+        }
+        long result = 0;
+
+        try {
+            Long value = freqTable.get(v);
+            if (value != null) {
+                result = value.longValue();
+            }
+        } catch (ClassCastException ex) {
+            return result;   // v is not comparable
+        }
+
+        if (c.compare(v, freqTable.firstKey()) < 0) {
+            return 0;  // v is comparable, but less than first value
+        }
+
+        if (c.compare(v, freqTable.lastKey()) >= 0) {
+            return getSumFreq();    // v is comparable, but greater than the last value
+        }
+
+        Iterator<Comparable<?>> values = valuesIterator();
+        while (values.hasNext()) {
+            Comparable<?> nextValue = values.next();
+            if (c.compare(v, nextValue) > 0) {
+                result += getCount(nextValue);
+            } else {
+                return result;
+            }
+        }
+        return result;
+    }
+
+     /**
+     * Returns the cumulative frequency of values less than or equal to v.
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     */
+    public long getCumFreq(int v) {
+        return getCumFreq(Long.valueOf(v));
+    }
+
+     /**
+     * Returns the cumulative frequency of values less than or equal to v.
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     */
+    public long getCumFreq(long v) {
+        return getCumFreq(Long.valueOf(v));
+    }
+
+    /**
+     * Returns the cumulative frequency of values less than or equal to v.
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values equal to v
+     */
+    public long getCumFreq(char v) {
+        return getCumFreq(Character.valueOf(v));
+    }
+
+    //----------------------------------------------------------------------------------------------
+
+    /**
+     * Returns the cumulative percentage of values less than or equal to v
+     * (as a proportion between 0 and 1).
+     * <p>
+     * Returns <code>Double.NaN</code> if no values have been added.
+     * Returns 0 if at least one value has been added, but v is not comparable
+     * to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values less than or equal to v
+     * @deprecated replaced by {@link #getCumPct(Comparable)} as of 2.0
+     */
+    @Deprecated
+    public double getCumPct(Object v) {
+        return getCumPct((Comparable<?>) v);
+
+    }
+
+    /**
+     * Returns the cumulative percentage of values less than or equal to v
+     * (as a proportion between 0 and 1).
+     * <p>
+     * Returns <code>Double.NaN</code> if no values have been added.
+     * Returns 0 if at least one value has been added, but v is not comparable
+     * to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values less than or equal to v
+     */
+    public double getCumPct(Comparable<?> v) {
+        final long sumFreq = getSumFreq();
+        if (sumFreq == 0) {
+            return Double.NaN;
+        }
+        return (double) getCumFreq(v) / (double) sumFreq;
+    }
+
+    /**
+     * Returns the cumulative percentage of values less than or equal to v
+     * (as a proportion between 0 and 1).
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values less than or equal to v
+     */
+    public double getCumPct(int v) {
+        return getCumPct(Long.valueOf(v));
+    }
+
+    /**
+     * Returns the cumulative percentage of values less than or equal to v
+     * (as a proportion between 0 and 1).
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values less than or equal to v
+     */
+    public double getCumPct(long v) {
+        return getCumPct(Long.valueOf(v));
+    }
+
+    /**
+     * Returns the cumulative percentage of values less than or equal to v
+     * (as a proportion between 0 and 1).
+     * <p>
+     * Returns 0 if v is not comparable to the values set.</p>
+     *
+     * @param v the value to lookup
+     * @return the proportion of values less than or equal to v
+     */
+    public double getCumPct(char v) {
+        return getCumPct(Character.valueOf(v));
+    }
+
+    /**
+     * A Comparator that compares comparable objects using the
+     * natural order.  Copied from Commons Collections ComparableComparator.
+     */
+    private static class NaturalComparator<T extends Comparable<T>> implements Comparator<Comparable<T>>, Serializable {
+
+        /** Serializable version identifier */
+        private static final long serialVersionUID = -3852193713161395148L;
+
+        /**
+         * Compare the two {@link Comparable Comparable} arguments.
+         * This method is equivalent to:
+         * <pre>(({@link Comparable Comparable})o1).{@link Comparable#compareTo compareTo}(o2)</pre>
+         *
+         * @param  o1 the first object
+         * @param  o2 the second object
+         * @return  result of comparison
+         * @throws NullPointerException when <i>o1</i> is <code>null</code>,
+         *         or when <code>((Comparable)o1).compareTo(o2)</code> does
+         * @throws ClassCastException when <i>o1</i> is not a {@link Comparable Comparable},
+         *         or when <code>((Comparable)o1).compareTo(o2)</code> does
+         */
+        @SuppressWarnings("unchecked") // cast to (T) may throw ClassCastException, see Javadoc
+        public int compare(Comparable<T> o1, Comparable<T> o2) {
+            return o1.compareTo((T) o2);
+        }
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result +
+                 ((freqTable == null) ? 0 : freqTable.hashCode());
+        return result;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (!(obj instanceof Frequency))
+            return false;
+        Frequency other = (Frequency) obj;
+        if (freqTable == null) {
+            if (other.freqTable != null)
+                return false;
+        } else if (!freqTable.equals(other.freqTable))
+            return false;
+        return true;
+    }
+
+}