Top Description Fields Constructors Methods
java.util

public Class DoubleSummaryStatistics

extends Object
implements DoubleConsumer
Class Inheritance
All Implemented Interfaces
java.util.function.DoubleConsumer
Imports
java.util.function.DoubleConsumer, java.util.stream.Collector, .DoubleStream
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.

This implementation does not check for overflow of the count.

Since
1.8

Field Summary

Modifier and TypeField and Description
private long
count

private double
max

private double
min

private double
simpleSum

private double
sum

private double
sumCompensation

Constructor Summary

AccessConstructor and Description
public
DoubleSummaryStatistics()

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

public
DoubleSummaryStatistics(long
the count of values
count, double
the minimum value
min, double
the maximum value
max, double
the sum of all values
sum)

Constructs a non-empty instance with the specified count, min, max, and sum.

Method Summary

Modifier and TypeMethod and Description
public void
accept(double
the input value
value)

Implements java.util.function.DoubleConsumer.accept.

Records another value into the summary information.

public void
combine(DoubleSummaryStatistics
another DoubleSummaryStatistics
other)

Combines the state of another DoubleSummaryStatistics into this one.

public final double

Returns:

the arithmetic mean of values, or zero if none
getAverage()

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

public final long

Returns:

the count of values
getCount()

Return the count of values recorded.

public final double

Returns:

the maximum recorded value, Double.NaN if any recorded value was NaN or Double.NEGATIVE_INFINITY if no values were recorded
getMax()

Returns the maximum recorded value, Double.NaN if any recorded value was NaN or Double.NEGATIVE_INFINITY if no values were recorded.

public final double

Returns:

the minimum recorded value, Double.NaN if any recorded value was NaN or Double.POSITIVE_INFINITY if no values were recorded
getMin()

Returns the minimum recorded value, Double.NaN if any recorded value was NaN or Double.POSITIVE_INFINITY if no values were recorded.

public final double

Returns:

the sum of values, or zero if none
getSum()

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

private void
sumWithCompensation(double value)

Incorporate a new double value using Kahan summation / compensated summation.

public String
toString()

Overrides java.lang.Object.toString.

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

Inherited from java.lang.Object:
cloneequalsfinalizegetClasshashCodenotifynotifyAllwaitwaitwait

Field Detail

countback to summary
private long count
maxback to summary
private double max
minback to summary
private double min
simpleSumback to summary
private double simpleSum
sumback to summary
private double sum
sumCompensationback to summary
private double sumCompensation

Constructor Detail

DoubleSummaryStatisticsback to summary
public DoubleSummaryStatistics()

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

DoubleSummaryStatisticsback to summary
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:long

the count of values

min:double

the minimum value

max:double

the maximum value

sum:double

the sum of all values

Exceptions
IllegalArgumentException:
if the arguments are inconsistent
Since
10

Method Detail

acceptback to summary
public void accept(double value)

Implements java.util.function.DoubleConsumer.accept.

Records another value into the summary information.

Parameters
value:double

the input value

Annotations
@Override
combineback to summary
public void combine(DoubleSummaryStatistics other)

Combines the state of another DoubleSummaryStatistics into this one.

Parameters
other:DoubleSummaryStatistics

another DoubleSummaryStatistics

Exceptions
NullPointerException:
if other is null
getAverageback to summary
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:double

the arithmetic mean of values, or zero if none

getCountback to summary
public final long getCount()

Return the count of values recorded.

Returns:long

the count of values

getMaxback to summary
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

getMinback to summary
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

getSumback to summary
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:double

the sum of values, or zero if none

sumWithCompensationback to summary
private void sumWithCompensation(double value)

Incorporate a new double value using Kahan summation / compensated summation.

toStringback to summary
public String toString()

Overrides java.lang.Object.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.

Returns:String

Doc from java.lang.Object.toString.

a string representation of the object

Annotations
@Override