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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.

This class is designed to work with (though does not require) streams. For example, you can compute summary statistics on a stream of longs with: 
 
LongSummaryStatistics stats = longStream.collect(LongSummaryStatistics::new,
                                                 LongSummaryStatistics::accept,
                                                 LongSummaryStatistics::combine);



LongSummaryStatistics can be used as a Stream.collect(Collector) reduction} target for a stream. For example: 
 
LongSummaryStatistics stats = people.stream()
                                    .collect(Collectors.summarizingLong(Person::getAge));


This computes, in a single pass, the count of people, as well as the minimum,
maximum, sum, and average of their ages.

Implementation Note:This implementation is not thread safe. However, it is safe to use 
Collectors.toLongStatistics() on a parallel stream, because the parallel implementation of Stream.collect() provides the necessary partitioning, isolation, and merging of results for safe and efficient parallel execution. 
This implementation does not check for overflow of the sum.
Since:1.8
/**
 * 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.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, Long.MAX_VALUE min, Long.MIN_VALUE max and zero average. 
/**
     * 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 int value into the summary information. 
Params:
  • value – the input value
/**
     * 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 long value into the summary information. 
Params:
  • value – the input 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 LongSummaryStatistics into this one. 
Params:
  • other – another LongSummaryStatistics
Throws:
/**
     * 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.

Returns:the count of values
/**
     * 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.

Returns:the sum of values, or zero if none
/**
     * 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 Long.MAX_VALUE if no values have been recorded. 
Returns:the minimum value, or Long.MAX_VALUE if none
/**
     * 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 Long.MIN_VALUE if no values have been recorded 
Returns:the maximum value, or Long.MIN_VALUE if none
/**
     * 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.

Returns:The arithmetic mean of values, or zero if none
/**
     * 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;
    }

    @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=%f, max=%d}",
            this.getClass().getSimpleName(),
            getCount(),
            getSum(),
            getMin(),
            getAverage(),
            getMax());
    }
}