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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.util;

import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
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 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#collect(Collector) reduction}
 * target for a {@linkplain java.util.stream.Stream stream}. For example:
 *
 * <pre> {@code
 * LongSummaryStatistics stats = people.stream()
 * .collect(Collectors.summarizingLong(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.
 *
 * @implNote This implementation is not thread safe. However, it is safe to use
 * {@link java.util.stream.Collectors#summarizingLong(java.util.function.ToLongFunction)
 * Collectors.summarizingLong()} 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;

 /**
 * Constructs an empty instance with zero count, zero sum,
 * {@code Long.MAX_VALUE} min, {@code Long.MIN_VALUE} max and zero
 * average.
 */
 public LongSummaryStatistics() { }

 /**
 * Constructs a non-empty instance with the specified {@code count},
 * {@code min}, {@code max}, and {@code sum}.
 *
 * <p>If {@code count} is zero then the remaining arguments are ignored and
 * an empty instance is constructed.
 *
 * <p>If the arguments are inconsistent then an {@code IllegalArgumentException}
 * is thrown. The necessary consistent argument conditions are:
 * <ul>
 * <li>{@code count >= 0}</li>
 * <li>{@code min <= max}</li>
 * </ul>
 * @apiNote
 * The enforcement of argument correctness means that the retrieved set of
 * recorded values obtained from a {@code LongSummaryStatistics} source
 * instance may not be a legal set of arguments for this constructor due to
 * arithmetic overflow of the source's recorded count of values.
 * The consistent argument conditions are not sufficient to prevent the
 * creation of an internally inconsistent instance. An example of such a
 * state would be an instance with: {@code count} = 2, {@code min} = 1,
 * {@code max} = 2, and {@code sum} = 0.
 *
 * @param count the count of values
 * @param min the minimum value
 * @param max the maximum value
 * @param sum the sum of all values
 * @throws IllegalArgumentException if the arguments are inconsistent
 * @since 10
 */
 public LongSummaryStatistics(long count, long min, long max, long sum)
 throws IllegalArgumentException {
 if (count < 0L) {
 throw new IllegalArgumentException("Negative count value");
 } else if (count > 0L) {
 if (min > max) throw new IllegalArgumentException("Minimum greater than maximum");

 this.count = count;
 this.sum = sum;
 this.min = min;
 this.max = max;
 }
 // Use default field values if count == 0
 }

 /**
 * 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 arithmetic mean of values recorded, or zero if no values have been
 * recorded.
 *
 * @return The arithmetic mean of values, or zero if none
 */
 public final double getAverage() {
 return getCount() > 0 ? (double) 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=%d, min=%d, average=%f, max=%d}",
 this.getClass().getSimpleName(),
 getCount(),
 getSum(),
 getMin(),
 getAverage(),
 getMax());
 }
}