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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.math4.legacy.stat.descriptive.rank;
18  
19  import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException;
20  import org.apache.commons.math4.legacy.exception.NullArgumentException;
21  import org.apache.commons.math4.legacy.stat.descriptive.AbstractStorelessUnivariateStatistic;
22  import org.apache.commons.math4.legacy.core.MathArrays;
23  
24  /**
25   * Returns the maximum of the available values.
26   * <ul>
27   * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
28   * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
29   * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
30   * the result is <code>Double.POSITIVE_INFINITY.</code></li>
31   * </ul>
32  * <p>
33   * <strong>Note that this implementation is not synchronized.</strong> If
34   * multiple threads access an instance of this class concurrently, and at least
35   * one of the threads invokes the <code>increment()</code> or
36   * <code>clear()</code> method, it must be synchronized externally.</p>
37   */
38  public class Max extends AbstractStorelessUnivariateStatistic {
39      /** Number of values that have been added. */
40      private long n;
41  
42      /** Current value of the statistic. */
43      private double value;
44  
45      /**
46       * Create a Max instance.
47       */
48      public Max() {
49          n = 0;
50          value = Double.NaN;
51      }
52  
53      /**
54       * Copy constructor, creates a new {@code Max} identical
55       * to the {@code original}.
56       *
57       * @param original the {@code Max} instance to copy
58       * @throws NullArgumentException if original is null
59       */
60      public Max(Max original) throws NullArgumentException {
61          copy(original, this);
62      }
63  
64      /**
65       * {@inheritDoc}
66       */
67      @Override
68      public void increment(final double d) {
69          if (d > value || Double.isNaN(value)) {
70              value = d;
71          }
72          n++;
73      }
74  
75      /**
76       * {@inheritDoc}
77       */
78      @Override
79      public void clear() {
80          value = Double.NaN;
81          n = 0;
82      }
83  
84      /**
85       * {@inheritDoc}
86       */
87      @Override
88      public double getResult() {
89          return value;
90      }
91  
92      /**
93       * {@inheritDoc}
94       */
95      @Override
96      public long getN() {
97          return n;
98      }
99  
100     /**
101      * Returns the maximum of the entries in the specified portion of
102      * the input array, or <code>Double.NaN</code> if the designated subarray
103      * is empty.
104      * <p>
105      * Throws <code>MathIllegalArgumentException</code> if the array is null or
106      * the array index parameters are not valid.</p>
107      * <ul>
108      * <li>The result is <code>NaN</code> iff all values are <code>NaN</code>
109      * (i.e. <code>NaN</code> values have no impact on the value of the statistic).</li>
110      * <li>If any of the values equals <code>Double.POSITIVE_INFINITY</code>,
111      * the result is <code>Double.POSITIVE_INFINITY.</code></li>
112      * </ul>
113      *
114      * @param values the input array
115      * @param begin index of the first array element to include
116      * @param length the number of elements to include
117      * @return the maximum of the values or Double.NaN if length = 0
118      * @throws MathIllegalArgumentException if the array is null or the array index
119      *  parameters are not valid
120      */
121     @Override
122     public double evaluate(final double[] values, final int begin, final int length)
123         throws MathIllegalArgumentException {
124 
125         double max = Double.NaN;
126         if (MathArrays.verifyValues(values, begin, length)) {
127             max = values[begin];
128             for (int i = begin; i < begin + length; i++) {
129                 if (!Double.isNaN(values[i])) {
130                     max = (max > values[i]) ? max : values[i];
131                 }
132             }
133         }
134         return max;
135     }
136 
137     /**
138      * {@inheritDoc}
139      */
140     @Override
141     public Max copy() {
142         Max result = new Max();
143         // No try-catch or advertised exception because args are non-null
144         copy(this, result);
145         return result;
146     }
147 
148     /**
149      * Copies source to dest.
150      * <p>Neither source nor dest can be null.</p>
151      *
152      * @param source Max to copy
153      * @param dest Max to copy to
154      * @throws NullArgumentException if either source or dest is null
155      */
156     public static void copy(Max source, Max dest)
157         throws NullArgumentException {
158         NullArgumentException.check(source);
159         NullArgumentException.check(dest);
160         dest.n = source.n;
161         dest.value = source.value;
162     }
163 }