Added in API level 24

Summary: Ctors | Methods | Inherited Methods

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() 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 non-empty instance with the specified count, min, max, and sum.

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

Inherited methods
From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
From interface java.util.function.DoubleConsumer abstract void accept(double value) Performs this operation on the given argument. default DoubleConsumer andThen(DoubleConsumer after) Returns a composed DoubleConsumer that performs, in sequence, this operation followed by the after operation.

Public constructors

DoubleSummaryStatistics

Added in API level 24

public DoubleSummaryStatistics ()

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

DoubleSummaryStatistics

Added in API level 34

public DoubleSummaryStatistics (long count, 
                double min, 
                double max, 
                double sum)

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

Throws
IllegalArgumentException	if the arguments are inconsistent

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.

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

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.

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

toString

Added in API level 24

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.

Returns
String	a string representation of the object.