8010953: Add primitive summary statistics utils

Reviewed-by: mduigou, dholmes, chegar, darcy
Contributed-by: NBrian Goetz <brian.goetz@oracle.com>

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

+/*
+ * Copyright (c) 2012, 2013, 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;
+
+/**
+ * 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#reduce(java.util.function.BinaryOperator) reduction}
+ * target for a {@linkplain java.util.stream.Stream stream}. For example:
+ *
+ * <pre> {@code
+ * DoubleSummaryStatistics stats = people.stream()
+ *     .collect(Collectors.toDoubleSummaryStatistics(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#toDoubleSummaryStatistics(java.util.function.ToDoubleFunction)
+ * Collectors.toDoubleStatistics()} 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 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;
+        sum += 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;
+        sum += other.sum;
+        min = Math.min(min, other.min);
+        max = Math.max(max, other.max);
+    }
+
+    /**
+     * 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. The sum returned can vary depending upon the order in which
+     * values are recorded. This is due to accumulated rounding error in
+     * addition of values of differing magnitudes. Values sorted by increasing
+     * absolute magnitude tend to yield more accurate results.  If any recorded
+     * value is a {@code NaN} or the sum is at any point a {@code NaN} then the
+     * sum will be {@code NaN}.
+     *
+     * @return the sum of values, or zero if none
+     */
+    public final double getSum() {
+        return sum;
+    }
+
+    /**
+     * 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 average of values recorded, or zero if no values have been
+     * recorded. The average returned can vary depending upon the order in
+     * which values are recorded. This is due to accumulated rounding error in
+     * addition of values of differing magnitudes. Values sorted by increasing
+     * absolute magnitude tend to yield more accurate results. If any recorded
+     * value is a {@code NaN} or the sum is at any point a {@code NaN} then the
+     * average will be {@code NaN}.
+     *
+     * @return the average of values, or zero if none
+     */
+    public final double getAverage() {
+        return getCount() > 0 ? getSum() / getCount() : 0.0d;
+    }
+
+    /**
+     * {@inheritDoc}
+     *
+     * 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());
+    }
+}

src/share/classes/java/util/IntSummaryStatistics.java

+/*
+ * Copyright (c) 2012, 2013, 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.IntConsumer;
+
+/**
+ * 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 ints with:
+ * <pre> {@code
+ * IntSummaryStatistics stats = intStream.collect(IntSummaryStatistics::new,
+ *     IntSummaryStatistics::accept,
+ *     IntSummaryStatistics::combine);
+ * }</pre>
+ *
+ * <p>{@code IntSummaryStatistics} can be used as a
+ * {@linkplain java.util.stream.Stream#reduce(java.util.function.BinaryOperator) reduction}
+ * target for a {@linkplain java.util.stream.Stream stream}. For example:
+ *
+ * <pre> {@code
+ * IntSummaryStatistics stats = people.stream()
+ *     .collect(Collectors.toIntSummaryStatistics(Person::getDependents));
+ *}</pre>
+ *
+ * This computes, in a single pass, the count of people, as well as the minimum,
+ * maximum, sum, and average of their number of dependents.
+ *
+ * @implNote This implementation is not thread safe. However, it is safe to use
+ * {@link java.util.stream.Collectors#toIntSummaryStatistics(java.util.function.ToIntFunction)
+ * Collectors.toIntStatistics()} 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.
+ *
+ * <p>This implementation does not check for overflow of the sum.
+ * @since 1.8
+ */
+public class IntSummaryStatistics implements IntConsumer {
+    private long count;
+    private long sum;
+    private int min = Integer.MAX_VALUE;
+    private int max = Integer.MIN_VALUE;
+
+    /**
+     * Construct an empty instance with zero count, zero sum,
+     * {@code Integer.MAX_VALUE} min, {@code Integer.MIN_VALUE} max and zero
+     * average.
+     */
+    public IntSummaryStatistics() { }
+
+    /**
+     * Records a new value into the summary information
+     *
+     * @param value the input value
+     */
+    @Override
+    public void accept(int value) {
+        ++count;
+        sum += value;
+        min = Math.min(min, value);
+        max = Math.max(max, value);
+    }
+
+    /**
+     * Combines the state of another {@code IntSummaryStatistics} into this one.
+     *
+     * @param other another {@code IntSummaryStatistics}
+     * @throws NullPointerException if {@code other} is null
+     */
+    public void combine(IntSummaryStatistics other) {
+        count += other.count;
+        sum += other.sum;
+        min = Math.min(min, other.min);
+        max = Math.max(max, other.max);
+    }
+
+    /**
+     * Returns 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.
+     *
+     * @return the sum of values, or zero if none
+     */
+    public final long getSum() {
+        return sum;
+    }
+
+    /**
+     * Returns the minimum value recorded, or {@code Integer.MAX_VALUE} if no
+     * values have been recorded.
+     *
+     * @return the minimum value, or {@code Integer.MAX_VALUE} if none
+     */
+    public final int getMin() {
+        return min;
+    }
+
+    /**
+     * Returns the maximum value recorded, or {@code Integer.MIN_VALUE} if no
+     * values have been recorded.
+     *
+     * @return the maximum value, or {@code Integer.MIN_VALUE} if none
+     */
+    public final int getMax() {
+        return max;
+    }
+
+    /**
+     * Returns the average of values recorded, or zero if no values have been
+     * recorded.
+     *
+     * @return the average of values, or zero if none
+     */
+    public final double getAverage() {
+        return getCount() > 0 ? (double) getSum() / getCount() : 0.0d;
+    }
+
+    @Override
+    /**
+     * {@inheritDoc}
+     *
+     * 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.
+     */
+    public String toString() {
+        return String.format(
+            "%s{count=%d, sum=%d, min=%d, average=%d, max=%d}",
+            this.getClass().getSimpleName(),
+            getCount(),
+            getSum(),
+            getMin(),
+            getAverage(),
+            getMax());
+    }
+}

src/share/classes/java/util/LongSummaryStatistics.java

+/*
+ * Copyright (c) 2012, 2013, 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.IntConsumer;
+import java.util.function.LongConsumer;
+
+/**
+ * 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 longs with:
+ * <pre> {@code
+ * LongSummaryStatistics stats = longStream.collect(LongSummaryStatistics::new,
+ *     LongSummaryStatistics::accept,
+ *     LongSummaryStatistics::combine);
+ * }</pre>
+ *
+ * <p>{@code LongSummaryStatistics} can be used as a
+ * {@linkplain java.util.stream.Stream#reduce(java.util.function.BinaryOperator) reduction}
+ * target for a {@linkplain java.util.stream.Stream stream}. For example:
+ *
+ * <pre> {@code
+ * LongSummaryStatistics stats = people.stream()
+ *     .collect(Collectors.toLongSummaryStatistics(Person::getAge));
+ *}</pre>
+ *
+ * This computes, in a single pass, the count of people, as well as the minimum,
+ * maximum, sum, and average of their ages in milliseconds.
+ *
+ * @implNote This implementation is not thread safe. However, it is safe to use
+ * {@link java.util.stream.Collectors#toLongSummaryStatistics(java.util.function.ToLongFunction)
+ * Collectors.toLongStatistics()} 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.
+ *
+ * <p>This implementation does not check for overflow of the sum.
+ * @since 1.8
+ */
+public class LongSummaryStatistics implements LongConsumer, IntConsumer {
+    private long count;
+    private long sum;
+    private long min = Long.MAX_VALUE;
+    private long max = Long.MIN_VALUE;
+
+    /**
+     * Construct an empty instance with zero count, zero sum,
+     * {@code Long.MAX_VALUE} min, {@code Long.MIN_VALUE} max and zero
+     * average.
+     */
+    public LongSummaryStatistics() { }
+
+    /**
+     * Records a new {@code int} value into the summary information.
+     *
+     * @param value the input value
+     */
+    @Override
+    public void accept(int value) {
+        accept((long) value);
+    }
+
+    /**
+     * Records a new {@code long} value into the summary information.
+     *
+     * @param value the input value
+     */
+    @Override
+    public void accept(long value) {
+        ++count;
+        sum += value;
+        min = Math.min(min, value);
+        max = Math.max(max, value);
+    }
+
+    /**
+     * Combines the state of another {@code LongSummaryStatistics} into this
+     * one.
+     *
+     * @param other another {@code LongSummaryStatistics}
+     * @throws NullPointerException if {@code other} is null
+     */
+    public void combine(LongSummaryStatistics other) {
+        count += other.count;
+        sum += other.sum;
+        min = Math.min(min, other.min);
+        max = Math.max(max, other.max);
+    }
+
+    /**
+     * Returns 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.
+     *
+     * @return the sum of values, or zero if none
+     */
+    public final long getSum() {
+        return sum;
+    }
+
+    /**
+     * Returns the minimum value recorded, or {@code Long.MAX_VALUE} if no
+     * values have been recorded.
+     *
+     * @return the minimum value, or {@code Long.MAX_VALUE} if none
+     */
+    public final long getMin() {
+        return min;
+    }
+
+    /**
+     * Returns the maximum value recorded, or {@code Long.MIN_VALUE} if no
+     * values have been recorded
+     *
+     * @return the maximum value, or {@code Long.MIN_VALUE} if none
+     */
+    public final long getMax() {
+        return max;
+    }
+
+    /**
+     * Returns the average of values recorded, or zero if no values have been
+     * recorded.
+     *
+     * @return The average of values, or zero if none
+     */
+    public final double getAverage() {
+        return getCount() > 0 ? (double) getSum() / getCount() : 0.0d;
+    }
+
+    @Override
+    /**
+     * {@inheritDoc}
+     *
+     * 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.
+     */
+    public String toString() {
+        return String.format(
+            "%s{count=%d, sum=%d, min=%d, average=%d, max=%d}",
+            this.getClass().getSimpleName(),
+            getCount(),
+            getSum(),
+            getMin(),
+            getAverage(),
+            getMax());
+    }
+}