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 */
017package org.apache.commons.statistics.descriptive;
018
019import java.math.BigInteger;
020
021/**
022 * Returns the maximum of the available values. Uses {@link Math#max(int, int) Math.max} as an
023 * underlying function to compute the {@code maximum}.
024 *
025 * <ul>
026 *   <li>The result is {@link Integer#MIN_VALUE} if no values are added.
027 * </ul>
028 *
029 * <p>This class is designed to work with (though does not require)
030 * {@linkplain java.util.stream streams}.
031 *
032 * <p><strong>This implementation is not thread safe.</strong>
033 * If multiple threads access an instance of this class concurrently,
034 * and at least one of the threads invokes the {@link java.util.function.IntConsumer#accept(int) accept} or
035 * {@link StatisticAccumulator#combine(StatisticResult) combine} method, it must be synchronized externally.
036 *
037 * <p>However, it is safe to use {@link java.util.function.IntConsumer#accept(int) accept}
038 * and {@link StatisticAccumulator#combine(StatisticResult) combine}
039 * as {@code accumulator} and {@code combiner} functions of
040 * {@link java.util.stream.Collector Collector} on a parallel stream,
041 * because the parallel implementation of {@link java.util.stream.Stream#collect Stream.collect()}
042 * provides the necessary partitioning, isolation, and merging of results for
043 * safe and efficient parallel execution.
044 *
045 * @since 1.1
046 * @see Math#max(int, int)
047 */
048public final class IntMax implements IntStatistic, StatisticAccumulator<IntMax> {
049
050    /** Current maximum. */
051    private int maximum = Integer.MIN_VALUE;
052
053    /**
054     * Create an instance.
055     */
056    private IntMax() {
057        // No-op
058    }
059
060    /**
061     * Creates an instance.
062     *
063     * <p>The initial result is {@link Integer#MIN_VALUE}.
064     *
065     * @return {@code IntMax} instance.
066     */
067    public static IntMax create() {
068        return new IntMax();
069    }
070
071    /**
072     * Returns an instance populated using the input {@code values}.
073     *
074     * <p>When the input is an empty array, the result is
075     * {@link Integer#MIN_VALUE}.
076     *
077     * @param values Values.
078     * @return {@code IntMax} instance.
079     */
080    public static IntMax of(int... values) {
081        return Statistics.add(new IntMax(), values);
082    }
083
084    /**
085     * Returns an instance populated using the specified range of {@code values}.
086     *
087     * <p>When the range is empty, the result is
088     * {@link Integer#MIN_VALUE}.
089     *
090     * @param values Values.
091     * @param from Inclusive start of the range.
092     * @param to Exclusive end of the range.
093     * @return {@code IntMax} instance.
094     * @throws IndexOutOfBoundsException if the sub-range is out of bounds
095     * @since 1.2
096     */
097    public static IntMax ofRange(int[] values, int from, int to) {
098        Statistics.checkFromToIndex(from, to, values.length);
099        return createFromRange(values, from, to);
100    }
101
102    /**
103     * Create an instance using the specified range of {@code values}.
104     *
105     * <p>Warning: No range checks are performed.
106     *
107     * @param values Values.
108     * @param from Inclusive start of the range.
109     * @param to Exclusive end of the range.
110     * @return {@code IntMax} instance.
111     */
112    static IntMax createFromRange(int[] values, int from, int to) {
113        return Statistics.add(new IntMax(), values, from, to);
114    }
115
116    /**
117     * Updates the state of the statistic to reflect the addition of {@code value}.
118     *
119     * @param value Value.
120     */
121    @Override
122    public void accept(int value) {
123        maximum = Math.max(maximum, value);
124    }
125
126    /**
127     * Gets the maximum of all input values.
128     *
129     * <p>When no values have been added, the result is
130     * {@link Integer#MIN_VALUE}.
131     *
132     * @return maximum of all values.
133     */
134    @Override
135    public int getAsInt() {
136        return maximum;
137    }
138
139    @Override
140    public long getAsLong() {
141        return maximum;
142    }
143
144    @Override
145    public double getAsDouble() {
146        return maximum;
147    }
148
149    @Override
150    public BigInteger getAsBigInteger() {
151        return BigInteger.valueOf(maximum);
152    }
153
154    @Override
155    public IntMax combine(IntMax other) {
156        accept(other.getAsInt());
157        return this;
158    }
159}