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.statistics.descriptive;
18
19 /**
20 * Returns the sum of the available values.
21 *
22 * <ul>
23 * <li>The result is zero if no values are added.
24 * <li>The result is {@code NaN} if any of the values is {@code NaN}.
25 * <li>The result is {@code NaN} if the values contain positive and negative infinity.
26 * <li>The result is non-finite if the values contain infinities of the same sign.
27 * </ul>
28 *
29 * <p>Note: In the event of infinite values of the same sign the result will be non-finite.
30 * In this case the returned results may differ (either the same infinity or {@code NaN}) based on
31 * input order if the sum of the finite-only values can overflow to an opposite signed infinity.
32 *
33 * <p>This class is designed to work with (though does not require)
34 * {@linkplain java.util.stream streams}.
35 *
36 * <p><strong>This instance is not thread safe.</strong>
37 * If multiple threads access an instance of this class concurrently,
38 * and at least one of the threads invokes the {@link java.util.function.DoubleConsumer#accept(double) accept} or
39 * {@link StatisticAccumulator#combine(StatisticResult) combine} method, it must be synchronized externally.
40 *
41 * <p>However, it is safe to use {@link java.util.function.DoubleConsumer#accept(double) accept}
42 * and {@link StatisticAccumulator#combine(StatisticResult) combine}
43 * as {@code accumulator} and {@code combiner} functions of
44 * {@link java.util.stream.Collector Collector} on a parallel stream,
45 * because the parallel instance of {@link java.util.stream.Stream#collect Stream.collect()}
46 * provides the necessary partitioning, isolation, and merging of results for
47 * safe and efficient parallel execution.
48 *
49 * @since 1.1
50 * @see org.apache.commons.numbers.core.Sum
51 */
52 public final class Sum implements DoubleStatistic, StatisticAccumulator<Sum> {
53
54 /** {@link org.apache.commons.numbers.core.Sum Sum} used to compute the sum. */
55 private final org.apache.commons.numbers.core.Sum delegate;
56
57 /**
58 * Create an instance.
59 */
60 private Sum() {
61 this(org.apache.commons.numbers.core.Sum.create());
62 }
63
64 /**
65 * Create an instance using the specified {@code sum}.
66 *
67 * @param sum Sum.
68 */
69 Sum(org.apache.commons.numbers.core.Sum sum) {
70 delegate = sum;
71 }
72
73 /**
74 * Creates an instance.
75 *
76 * <p>The initial result is zero.
77 *
78 * @return {@code Sum} instance.
79 */
80 public static Sum create() {
81 return new Sum();
82 }
83
84 /**
85 * Returns an instance populated using the input {@code values}.
86 *
87 * <p>The result is {@code NaN} if any of the values is {@code NaN}
88 * or the sum at any point is a {@code NaN}.
89 *
90 * <p>When the input is an empty array, the result is zero.
91 *
92 * @param values Values.
93 * @return {@code Sum} instance.
94 */
95 public static Sum of(double... values) {
96 return new Sum(org.apache.commons.numbers.core.Sum.of(values));
97 }
98
99 /**
100 * Updates the state of the statistic to reflect the addition of {@code value}.
101 *
102 * @param value Value.
103 */
104 @Override
105 public void accept(double value) {
106 delegate.accept(value);
107 }
108
109 /**
110 * Gets the sum of all input values.
111 *
112 * <p>When no values have been added, the result is zero.
113 *
114 * @return sum of all values.
115 */
116 @Override
117 public double getAsDouble() {
118 return delegate.getAsDouble();
119 }
120
121 @Override
122 public Sum combine(Sum other) {
123 delegate.add(other.delegate);
124 return this;
125 }
126 }