 All Implemented Interfaces:
DoubleConsumer
public class DoubleSummaryStatistics extends Object implements DoubleConsumer
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 ofStream.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

Constructor Summary
Constructors Constructor Description DoubleSummaryStatistics()
Constructs an empty instance with zero count, zero sum,Double.POSITIVE_INFINITY
min,Double.NEGATIVE_INFINITY
max and zero average.DoubleSummaryStatistics(long count, double min, double max, double sum)
Constructs a nonempty instance with the specifiedcount
,min
,max
, andsum
. 
Method Summary
Modifier and Type Method Description void
accept(double value)
Records another value into the summary information.void
combine(DoubleSummaryStatistics other)
Combines the state of anotherDoubleSummaryStatistics
into this one.double
getAverage()
Returns the arithmetic mean of values recorded, or zero if no values have been recorded.long
getCount()
Return the count of values recorded.double
getMax()
Returns the maximum recorded value,Double.NaN
if any recorded value was NaN orDouble.NEGATIVE_INFINITY
if no values were recorded.double
getMin()
Returns the minimum recorded value,Double.NaN
if any recorded value was NaN orDouble.POSITIVE_INFINITY
if no values were recorded.double
getSum()
Returns the sum of values recorded, or zero if no values have been recorded.String
toString()
Returns a nonempty string representation of this object suitable for debugging.Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods declared in interface java.util.function.DoubleConsumer
andThen

Constructor Details

DoubleSummaryStatistics
public DoubleSummaryStatistics()Constructs an empty instance with zero count, zero sum,Double.POSITIVE_INFINITY
min,Double.NEGATIVE_INFINITY
max and zero average. 
DoubleSummaryStatistics
public DoubleSummaryStatistics(long count, double min, double max, double sum) throws IllegalArgumentExceptionConstructs a nonempty instance with the specifiedcount
,min
,max
, andsum
.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, andsum
= 0.  Parameters:
count
 the count of valuesmin
 the minimum valuemax
 the maximum valuesum
 the sum of all values Throws:
IllegalArgumentException
 if the arguments are inconsistent Since:
 10


Method Details

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

combine
Combines the state of anotherDoubleSummaryStatistics
into this one. Parameters:
other
 anotherDoubleSummaryStatistics
 Throws:
NullPointerException
 ifother
is null

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

getSum
public final double getSum()Returns the sum of values recorded, or zero if no values have been recorded.The value of a floatingpoint 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 nonfinite sum being computed. This can occur even if the all the recorded values being summed are finite. If any recorded value is nonfinite, the sum will be nonfinite:
 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.
 API Note:
 Values sorted by increasing absolute magnitude tend to yield more accurate results.
 Returns:
 the sum of values, or zero if none

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

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

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

toString
Returns a nonempty string representation of this object suitable for debugging. The exact presentation format is unspecified and may vary between implementations and versions.
