Package Summary  Overview Summary

class:DoubleSummaryStatistics [NONE]

  • All Implemented Interfaces:
    DoubleConsumer

    public class DoubleSummaryStatistics
    extends Object
    implements DoubleConsumer
    
    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 doubles with:

     
    
    
     DoubleSummaryStatistics stats = doubleStream.collect(DoubleSummaryStatistics::new,
                                                          DoubleSummaryStatistics::accept,
                                                          DoubleSummaryStatistics::combine);
     
    

    DoubleSummaryStatistics can be used as a reduction target for a stream. For example:

     
    
    
     DoubleSummaryStatistics stats = people.stream()
         .collect(Collectors.summarizingDouble(Person::getWeight));
    
    
    This computes, in a single pass, the count of people, as well as the minimum, maximum, sum, and average of their weights.

    Implementation Note:
    This implementation is not thread safe. However, it is safe to use Collectors.summarizingDouble() 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.
    Since:
    1.8

constructor:<init>() [NONE]

  • DoubleSummaryStatistics

    public DoubleSummaryStatistics()
    Constructs an empty instance with zero count, zero sum, Double.POSITIVE_INFINITY min, Double.NEGATIVE_INFINITY max and zero average.

constructor:<init>(long,double,double,double) [NONE]

  • DoubleSummaryStatistics

    public DoubleSummaryStatistics​(long count,
                                   double min,
                                   double max,
                                   double 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 && !isNaN(sum)) || (isNaN(min) && isNaN(max) && isNaN(sum))

    API Note:
    The enforcement of argument correctness means that the retrieved set of recorded values obtained from a DoubleSummaryStatistics 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:accept(double) [NONE]

  • accept

    public void accept​(double value)
    Records another value into the summary information.
    Specified by:
    accept in interface DoubleConsumer
    Parameters:
    value - the input value

method:combine(java.util.DoubleSummaryStatistics) [NONE]

  • combine

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

method:getCount() [NONE]

  • getCount

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

method:getSum() [NONE]

  • getSum

    public final double getSum()
    Returns the sum of values recorded, or zero if no values have been recorded.

    The value of a floating-point sum is a function both of the input values as well as the order of addition operations. The order of addition operations of this method is intentionally not defined to allow for implementation flexibility to improve the speed and accuracy of the computed result. In particular, this method may be implemented using compensated summation or other technique to reduce the error bound in the numerical sum compared to a simple summation of double values. Because of the unspecified order of operations and the possibility of using differing summation schemes, the output of this method may vary on the same input values.

    Various conditions can result in a non-finite sum being computed. This can occur even if the all the recorded values being summed are finite. If any recorded value is non-finite, the sum will be non-finite:

    • If any recorded value is a NaN, then the final sum will be NaN.
    • If the recorded values contain one or more infinities, the sum will be infinite or NaN.
      • If the recorded values contain infinities of opposite sign, the sum will be NaN.
      • If the recorded values contain infinities of one sign and an intermediate sum overflows to an infinity of the opposite sign, the sum may be NaN.
    It is possible for intermediate sums of finite values to overflow into opposite-signed infinities; if that occurs, the final sum will be NaN even if the recorded values are all finite. If all the recorded values are zero, the sign of zero is not guaranteed to be preserved in the final sum.

    API Note:
    Values sorted by increasing absolute magnitude tend to yield more accurate results.
    Returns:
    the sum of values, or zero if none

method:getMin() [NONE]

  • getMin

    public final double getMin()
    Returns the minimum recorded value, Double.NaN if any recorded value was NaN or 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.
    Returns:
    the minimum recorded value, Double.NaN if any recorded value was NaN or Double.POSITIVE_INFINITY if no values were recorded

method:getMax() [NONE]

  • getMax

    public final double getMax()
    Returns the maximum recorded value, Double.NaN if any recorded value was NaN or 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.
    Returns:
    the maximum recorded value, Double.NaN if any recorded value was NaN or Double.NEGATIVE_INFINITY if no values were recorded

method:getAverage() [NONE]

  • getAverage

    public final double getAverage()
    Returns the arithmetic mean of values recorded, or zero if no values have been recorded.

    The computed average can vary numerically and have the special case behavior as computing the sum; see getSum() for details.

    API Note:
    Values sorted by increasing absolute magnitude tend to yield more accurate results.
    Returns:
    the arithmetic mean of values, or zero if none

method:toString() [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.

© 2019 Oracle Corporation and/or its affiliates