    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017    package org.apache.commons.math3.stat.descriptive.rank;
    018
    019    import java.io.Serializable;
    020
    021    import org.apache.commons.math3.exception.MathIllegalArgumentException;
    022    import org.apache.commons.math3.exception.NullArgumentException;
    023    import org.apache.commons.math3.stat.descriptive.AbstractStorelessUnivariateStatistic;
    024    import org.apache.commons.math3.util.MathUtils;
    025
    026    /**
    027     * Returns the maximum of the available values.
    028     * <p>
    029     * <ul>
    030     * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
    031     * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
    032     * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
    033     * the result is <code>Double.POSITIVE_INFINITY.</code></li>
    034     * </ul></p>
    035    * <p>
    036     * <strong>Note that this implementation is not synchronized.</strong> If
    037     * multiple threads access an instance of this class concurrently, and at least
    038     * one of the threads invokes the <code>increment()</code> or
    039     * <code>clear()</code> method, it must be synchronized externally.</p>
    040     *
    041     * @version $Id: Max.java 1416643 2012-12-03 19:37:14Z tn $
    042     */
    043    public class Max extends AbstractStorelessUnivariateStatistic implements Serializable {
    044
    045        /** Serializable version identifier */
    046        private static final long serialVersionUID = -5593383832225844641L;
    047
    048        /** Number of values that have been added */
    049        private long n;
    050
    051        /** Current value of the statistic */
    052        private double value;
    053
    054        /**
    055         * Create a Max instance
    056         */
    057        public Max() {
    058            n = 0;
    059            value = Double.NaN;
    060        }
    061
    062        /**
    063         * Copy constructor, creates a new {@code Max} identical
    064         * to the {@code original}
    065         *
    066         * @param original the {@code Max} instance to copy
    067         * @throws NullArgumentException if original is null
    068         */
    069        public Max(Max original) throws NullArgumentException {
    070            copy(original, this);
    071        }
    072
    073        /**
    074         * {@inheritDoc}
    075         */
    076        @Override
    077        public void increment(final double d) {
    078            if (d > value || Double.isNaN(value)) {
    079                value = d;
    080            }
    081            n++;
    082        }
    083
    084        /**
    085         * {@inheritDoc}
    086         */
    087        @Override
    088        public void clear() {
    089            value = Double.NaN;
    090            n = 0;
    091        }
    092
    093        /**
    094         * {@inheritDoc}
    095         */
    096        @Override
    097        public double getResult() {
    098            return value;
    099        }
    100
    101        /**
    102         * {@inheritDoc}
    103         */
    104        public long getN() {
    105            return n;
    106        }
    107
    108        /**
    109         * Returns the maximum of the entries in the specified portion of
    110         * the input array, or <code>Double.NaN</code> if the designated subarray
    111         * is empty.
    112         * <p>
    113         * Throws <code>MathIllegalArgumentException</code> if the array is null or
    114         * the array index parameters are not valid.</p>
    115         * <p>
    116         * <ul>
    117         * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
    118         * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
    119         * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
    120         * the result is <code>Double.POSITIVE_INFINITY.</code></li>
    121         * </ul></p>
    122         *
    123         * @param values the input array
    124         * @param begin index of the first array element to include
    125         * @param length the number of elements to include
    126         * @return the maximum of the values or Double.NaN if length = 0
    127         * @throws MathIllegalArgumentException if the array is null or the array index
    128         *  parameters are not valid
    129         */
    130        @Override
    131        public double evaluate(final double[] values, final int begin, final int length)
    132        throws MathIllegalArgumentException {
    133            double max = Double.NaN;
    134            if (test(values, begin, length)) {
    135                max = values[begin];
    136                for (int i = begin; i < begin + length; i++) {
    137                    if (!Double.isNaN(values[i])) {
    138                        max = (max > values[i]) ? max : values[i];
    139                    }
    140                }
    141            }
    142            return max;
    143        }
    144
    145        /**
    146         * {@inheritDoc}
    147         */
    148        @Override
    149        public Max copy() {
    150            Max result = new Max();
    151            // No try-catch or advertised exception because args are non-null
    152            copy(this, result);
    153            return result;
    154        }
    155
    156        /**
    157         * Copies source to dest.
    158         * <p>Neither source nor dest can be null.</p>
    159         *
    160         * @param source Max to copy
    161         * @param dest Max to copy to
    162         * @throws NullArgumentException if either source or dest is null
    163         */
    164        public static void copy(Max source, Max dest)
    165            throws NullArgumentException {
    166            MathUtils.checkNotNull(source);
    167            MathUtils.checkNotNull(dest);
    168            dest.setData(source.getDataRef());
    169            dest.n = source.n;
    170            dest.value = source.value;
    171        }
    172    }