8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/util/DoubleSummaryStatistics.java

@@ -0,0 +1,260 @@
+/*
+ * Copyright (c) 2012, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.util;
+
+import java.util.function.DoubleConsumer;
+import java.util.stream.Collector;
+
+/**
+ * A state object for collecting statistics such as count, min, max, sum, and
+ * average.
+ *
+ * <p>This class is designed to work with (though does not require)
+ * {@linkplain java.util.stream streams}. For example, you can compute
+ * summary statistics on a stream of doubles with:
+ * <pre> {@code
+ * DoubleSummaryStatistics stats = doubleStream.collect(DoubleSummaryStatistics::new,
+ *                                                      DoubleSummaryStatistics::accept,
+ *                                                      DoubleSummaryStatistics::combine);
+ * }</pre>
+ *
+ * <p>{@code DoubleSummaryStatistics} can be used as a
+ * {@linkplain java.util.stream.Stream#collect(Collector) reduction}
+ * target for a {@linkplain java.util.stream.Stream stream}. For example:
+ *
+ * <pre> {@code
+ * DoubleSummaryStatistics stats = people.stream()
+ *     .collect(Collectors.summarizingDouble(Person::getWeight));
+ *}</pre>
+ *
+ * This computes, in a single pass, the count of people, as well as the minimum,
+ * maximum, sum, and average of their weights.
+ *
+ * @implNote This implementation is not thread safe. However, it is safe to use
+ * {@link java.util.stream.Collectors#summarizingDouble(java.util.function.ToDoubleFunction)
+ * Collectors.summarizingDouble()} on a parallel stream, because the parallel
+ * implementation of {@link java.util.stream.Stream#collect Stream.collect()}
+ * provides the necessary partitioning, isolation, and merging of results for
+ * safe and efficient parallel execution.
+ * @since 1.8
+ */
+public class DoubleSummaryStatistics implements DoubleConsumer {
+    private long count;
+    private double sum;
+    private double sumCompensation; // Low order bits of sum
+    private double simpleSum; // Used to compute right sum for non-finite inputs
+    private double min = Double.POSITIVE_INFINITY;
+    private double max = Double.NEGATIVE_INFINITY;
+
+    /**
+     * Construct an empty instance with zero count, zero sum,
+     * {@code Double.POSITIVE_INFINITY} min, {@code Double.NEGATIVE_INFINITY}
+     * max and zero average.
+     */
+    public DoubleSummaryStatistics() { }
+
+    /**
+     * Records another value into the summary information.
+     *
+     * @param value the input value
+     */
+    @Override
+    public void accept(double value) {
+        ++count;
+        simpleSum += value;
+        sumWithCompensation(value);
+        min = Math.min(min, value);
+        max = Math.max(max, value);
+    }
+
+    /**
+     * Combines the state of another {@code DoubleSummaryStatistics} into this
+     * one.
+     *
+     * @param other another {@code DoubleSummaryStatistics}
+     * @throws NullPointerException if {@code other} is null
+     */
+    public void combine(DoubleSummaryStatistics other) {
+        count += other.count;
+        simpleSum += other.simpleSum;
+        sumWithCompensation(other.sum);
+        sumWithCompensation(other.sumCompensation);
+        min = Math.min(min, other.min);
+        max = Math.max(max, other.max);
+    }
+
+    /**
+     * Incorporate a new double value using Kahan summation /
+     * compensated summation.
+     */
+    private void sumWithCompensation(double value) {
+        double tmp = value - sumCompensation;
+        double velvel = sum + tmp; // Little wolf of rounding error
+        sumCompensation = (velvel - sum) - tmp;
+        sum = velvel;
+    }
+
+    /**
+     * Return the count of values recorded.
+     *
+     * @return the count of values
+     */
+    public final long getCount() {
+        return count;
+    }
+
+    /**
+     * Returns the sum of values recorded, or zero if no values have been
+     * recorded.
+     *
+     * <p> The value of a floating-point sum is a function both of the
+     * input values as well as the order of addition operations. The
+     * order of addition operations of this method is intentionally
+     * not defined to allow for implementation flexibility to improve
+     * the speed and accuracy of the computed result.
+     *
+     * In particular, this method may be implemented using compensated
+     * summation or other technique to reduce the error bound in the
+     * numerical sum compared to a simple summation of {@code double}
+     * values.
+     *
+     * Because of the unspecified order of operations and the
+     * possibility of using differing summation schemes, the output of
+     * this method may vary on the same input values.
+     *
+     * <p>Various conditions can result in a non-finite sum being
+     * computed. This can occur even if the all the recorded values
+     * being summed are finite. If any recorded value is non-finite,
+     * the sum will be non-finite:
+     *
+     * <ul>
+     *
+     * <li>If any recorded value is a NaN, then the final sum will be
+     * NaN.
+     *
+     * <li>If the recorded values contain one or more infinities, the
+     * sum will be infinite or NaN.
+     *
+     * <ul>
+     *
+     * <li>If the recorded values contain infinities of opposite sign,
+     * the sum will be NaN.
+     *
+     * <li>If the recorded values contain infinities of one sign and
+     * an intermediate sum overflows to an infinity of the opposite
+     * sign, the sum may be NaN.
+     *
+     * </ul>
+     *
+     * </ul>
+     *
+     * It is possible for intermediate sums of finite values to
+     * overflow into opposite-signed infinities; if that occurs, the
+     * final sum will be NaN even if the recorded values are all
+     * finite.
+     *
+     * If all the recorded values are zero, the sign of zero is
+     * <em>not</em> guaranteed to be preserved in the final sum.
+     *
+     * @apiNote Values sorted by increasing absolute magnitude tend to yield
+     * more accurate results.
+     *
+     * @return the sum of values, or zero if none
+     */
+    public final double getSum() {
+        // Better error bounds to add both terms as the final sum
+        double tmp =  sum + sumCompensation;
+        if (Double.isNaN(tmp) && Double.isInfinite(simpleSum))
+            // If the compensated sum is spuriously NaN from
+            // accumulating one or more same-signed infinite values,
+            // return the correctly-signed infinity stored in
+            // simpleSum.
+            return simpleSum;
+        else
+            return tmp;
+    }
+
+    /**
+     * Returns the minimum recorded value, {@code Double.NaN} if any recorded
+     * value was NaN or {@code Double.POSITIVE_INFINITY} if no values were
+     * recorded. Unlike the numerical comparison operators, this method
+     * considers negative zero to be strictly smaller than positive zero.
+     *
+     * @return the minimum recorded value, {@code Double.NaN} if any recorded
+     * value was NaN or {@code Double.POSITIVE_INFINITY} if no values were
+     * recorded
+     */
+    public final double getMin() {
+        return min;
+    }
+
+    /**
+     * Returns the maximum recorded value, {@code Double.NaN} if any recorded
+     * value was NaN or {@code Double.NEGATIVE_INFINITY} if no values were
+     * recorded. Unlike the numerical comparison operators, this method
+     * considers negative zero to be strictly smaller than positive zero.
+     *
+     * @return the maximum recorded value, {@code Double.NaN} if any recorded
+     * value was NaN or {@code Double.NEGATIVE_INFINITY} if no values were
+     * recorded
+     */
+    public final double getMax() {
+        return max;
+    }
+
+    /**
+     * Returns the arithmetic mean of values recorded, or zero if no
+     * values have been recorded.
+     *
+     * <p> The computed average can vary numerically and have the
+     * special case behavior as computing the sum; see {@link #getSum}
+     * for details.
+     *
+     * @apiNote Values sorted by increasing absolute magnitude tend to yield
+     * more accurate results.
+     *
+     * @return the arithmetic mean of values, or zero if none
+     */
+    public final double getAverage() {
+        return getCount() > 0 ? getSum() / getCount() : 0.0d;
+    }
+
+    /**
+     * Returns a non-empty string representation of this object suitable for
+     * debugging. The exact presentation format is unspecified and may vary
+     * between implementations and versions.
+     */
+    @Override
+    public String toString() {
+        return String.format(
+            "%s{count=%d, sum=%f, min=%f, average=%f, max=%f}",
+            this.getClass().getSimpleName(),
+            getCount(),
+            getSum(),
+            getMin(),
+            getAverage(),
+            getMax());
+    }
+}