Module java.base
Package java.util

Class LongSummaryStatistics

  • All Implemented Interfaces:
    IntConsumer, LongConsumer
    public class LongSummaryStatistics
extends Object
implements LongConsumer, IntConsumer
    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 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.summarizingLong() 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

    • Constructor Summary

      Constructors 
      Constructor Description
      LongSummaryStatistics()
      Constructs an empty instance with zero count, zero sum, Long.MAX_VALUE min, Long.MIN_VALUE max and zero average.
      LongSummaryStatistics​(long count, long min, long max, long sum)
      Constructs a non-empty instance with the specified count, min, max, and sum.

    • Method Summary

      Modifier and Type Method Description
      void accept​(int value)
      Records a new int value into the summary information.
      void accept​(long value)
      Records a new long value into the summary information.
      void combine​(LongSummaryStatistics other)
      Combines the state of another LongSummaryStatistics into this one.
      double getAverage()
      Returns the arithmetic mean of values recorded, or zero if no values have been recorded.
      long getCount()
      Returns the count of values recorded.
      long getMax()
      Returns the maximum value recorded, or Long.MIN_VALUE if no values have been recorded
      long getMin()
      Returns the minimum value recorded, or Long.MAX_VALUE if no values have been recorded.
      long getSum()
      Returns the sum of values recorded, or zero if no values have been recorded.
      String toString()
      Returns a non-empty string representation of this object suitable for debugging.

    • Constructor Detail

      • LongSummaryStatistics

        public LongSummaryStatistics()
        Constructs an empty instance with zero count, zero sum, Long.MAX_VALUE min, Long.MIN_VALUE max and zero average.

      • LongSummaryStatistics

        public LongSummaryStatistics​(long count,
                             long min,
                             long max,
                             long sum)
                      throws IllegalArgumentException
        Constructs a non-empty instance with the specified count, min, max, and sum.

        If count is zero then the remaining arguments are ignored and an empty instance is constructed.

        If the arguments are inconsistent then an IllegalArgumentException is thrown. The necessary consistent argument conditions are:

        • count >= 0
        • min <= max

        API Note:
        The enforcement of argument correctness means that the retrieved set of recorded values obtained from a 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: count = 2, min = 1, max = 2, and sum = 0.
        Parameters:
        count - the count of values
        min - the minimum value
        max - the maximum value
        sum - the sum of all values
        Throws:
        IllegalArgumentException - if the arguments are inconsistent
        Since:
        10

    • Method Detail

      • accept

        public void accept​(int value)
        Records a new int value into the summary information.
        Specified by:
        accept in interface IntConsumer
        Parameters:
        value - the input value

      • accept

        public void accept​(long value)
        Records a new long value into the summary information.
        Specified by:
        accept in interface LongConsumer
        Parameters:
        value - the input value

      • combine

        public void combine​(LongSummaryStatistics other)
        Combines the state of another LongSummaryStatistics into this one.
        Parameters:
        other - another LongSummaryStatistics
        Throws:
        NullPointerException - if other is null

      • getCount

        public final long getCount()
        Returns the count of values recorded.
        Returns:
        the count of values

      • getSum

        public final long getSum()
        Returns the sum of values recorded, or zero if no values have been recorded.
        Returns:
        the sum of values, or zero if none

      • getMin

        public final long getMin()
        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

      • getMax

        public final long getMax()
        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

      • getAverage

        public final double getAverage()
        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

      • toString

        public String toString()
        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.
        Overrides:
        toString in class Object
        Returns:
        a string representation of the object.