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package java.util;

import java.util.function.IntConsumer;
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 ints with: 
 
IntSummaryStatistics stats = intStream.collect(IntSummaryStatistics::new,
                                               IntSummaryStatistics::accept,
                                               IntSummaryStatistics::combine);



IntSummaryStatistics can be used as a reduction target for a stream. For example: 
 
IntSummaryStatistics stats = people.stream()
                                   .collect(Collectors.summarizingInt(Person::getDependents));


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

Implementation Note:This implementation is not thread safe. However, it is safe to use 
Collectors.toIntStatistics() 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 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#collect(Collector) reduction}
 * target for a {@linkplain java.util.stream.Stream stream}. For example:
 *
 * <pre> {@code
 * IntSummaryStatistics stats = people.stream()
 *                                    .collect(Collectors.summarizingInt(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#summarizingInt(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, Integer.MAX_VALUE min, Integer.MIN_VALUE max and zero average. 
/**
     * 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

Params:
  • value – the input value
/**
     * 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 IntSummaryStatistics into this one. 
Params:
  • other – another IntSummaryStatistics
Throws:
/**
     * 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.

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 Integer.MAX_VALUE if no values have been recorded. 
Returns:the minimum value, or Integer.MAX_VALUE if none
/**
     * 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 Integer.MIN_VALUE if no values have been recorded. 
Returns:the maximum value, or Integer.MIN_VALUE if none
/**
     * 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 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());
    }
}