DoubleSummaryStatistics

public class DoubleSummaryStatistics
extends Object implements DoubleConsumer

java.lang.Object
   ↳ java.util.DoubleSummaryStatistics


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.

Summary

Public constructors

DoubleSummaryStatistics()

Construct an empty instance with zero count, zero sum, Double.POSITIVE_INFINITY min, Double.NEGATIVE_INFINITY max and zero average.

Public methods

void accept(double value)

Records another value into the summary information.

void combine(DoubleSummaryStatistics other)

Combines the state of another DoubleSummaryStatistics into this one.

final double getAverage()

Returns the arithmetic mean of values recorded, or zero if no values have been recorded.

final long getCount()

Return the count of values recorded.

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.

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.

final double getSum()

Returns the sum of values recorded, or zero if no values have been recorded.

String toString()

Returns a string representation of the object. Returns a non-empty string representation of this object suitable for debugging.

Inherited methods

Public constructors

DoubleSummaryStatistics

added in API level 24
public DoubleSummaryStatistics ()

Construct an empty instance with zero count, zero sum, Double.POSITIVE_INFINITY min, Double.NEGATIVE_INFINITY max and zero average.

Public methods

accept

added in API level 24
public void accept (double value)

Records another value into the summary information.

Parameters
value double: the input value

combine

added in API level 24
public void combine (DoubleSummaryStatistics other)

Combines the state of another DoubleSummaryStatistics into this one.

Parameters
other DoubleSummaryStatistics: another DoubleSummaryStatistics

Throws
NullPointerException if other is null

getAverage

added in API level 24
public final double getAverage ()

Returns the arithmetic mean of values recorded, or zero if no values have been recorded. If any recorded value is a NaN or the sum is at any point a NaN then the average will be code NaN.

The average returned can vary depending upon the order in which values are recorded. This method may be implemented using compensated summation or other technique to reduce the error bound in the numerical sum used to compute the average.

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

getCount

added in API level 24
public final long getCount ()

Return the count of values recorded.

Returns
long the count of values

getMax

added in API level 24
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
double the maximum recorded value, Double.NaN if any recorded value was NaN or Double.NEGATIVE_INFINITY if no values were recorded

getMin

added in API level 24
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
double the minimum recorded value, Double.NaN if any recorded value was NaN or Double.POSITIVE_INFINITY if no values were recorded

getSum

added in API level 24
public final double getSum ()

Returns the sum of values recorded, or zero if no values have been recorded. If any recorded value is a NaN or the sum is at any point a NaN then the sum will be NaN.

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.

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

toString

added in API level 24
public String toString ()

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 
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.

Returns
String a string representation of the object.