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) {@linkplain java.util.stream 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
{@linkplain java.util.stream.Stream#collect(Collector) reduction}
target for a {@linkplain java.util.stream.Stream 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.
Public Constructor Summary
DoubleSummaryStatistics()
Construct an empty instance with zero count, zero sum,
Double.POSITIVE_INFINITY min, Double.NEGATIVE_INFINITY
max and zero average. |
Public Method Summary
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 containing a concise, human-readable description of this
object.
Returns a non-empty string representation of this object suitable for
debugging.
|
Inherited Method Summary
Public Constructors
public DoubleSummaryStatistics ()
Construct an empty instance with zero count, zero sum,
Double.POSITIVE_INFINITY
min, Double.NEGATIVE_INFINITY
max and zero average.
Public Methods
public void accept (double value)
Records another value into the summary information.
Parameters
value | the input value |
---|
public void combine (DoubleSummaryStatistics other)
Combines the state of another DoubleSummaryStatistics
into this
one.
Parameters
other | another DoubleSummaryStatistics |
---|
Throws
NullPointerException | if other is null
|
---|
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.
Returns
- the arithmetic mean of values, or zero if none
public final long getCount ()
Return the count of values recorded.
Returns
- the count of values
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 orDouble.NEGATIVE_INFINITY
if no values were recorded
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 orDouble.POSITIVE_INFINITY
if no values were recorded
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.
Returns
- the sum of values, or zero if none
public String toString ()
Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression:
getClass().getName() + '@' + Integer.toHexString(hashCode())
See Writing a useful
toString
method
if you intend implementing your own toString
method.
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
- a printable representation of this object.