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java.base / java.util
Class DoubleSummaryStatistics
java.lang.Object
  java.util.DoubleSummaryStatistics
All Implemented Interfaces:
DoubleConsumer

public class DoubleSummaryStatistics
extends Object
implements DoubleConsumer
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

Constructor Summary
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.
Method Summary
void
accept(double value)
Records another value into the summary information.
void
Combines the state of another DoubleSummaryStatistics into this one.
final double
Returns the arithmetic mean of values recorded, or zero if no values have been recorded.
final long
Return the count of values recorded.
final double
Returns the maximum recorded value, Double.NaN if any recorded value was NaN or Double.NEGATIVE_INFINITY if no values were recorded.
final double
Returns the minimum recorded value, Double.NaN if any recorded value was NaN or Double.POSITIVE_INFINITY if no values were recorded.
final double
Returns the sum of values recorded, or zero if no values have been recorded.
Returns a non-empty string representation of this object suitable for debugging.
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.function.DoubleConsumer
andThen
Constructor Detail
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
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:

Parameters:
count - the count of values
min - the minimum value
max - the maximum value
sum - the sum of all values
Throws:
IllegalArgumentException - if the arguments are inconsistent
Since:
10
Method Detail
accept
public void accept
(double value)
Records another value into the summary information.
Specified by:
accept in interface DoubleConsumer
Parameters:
value - the input value

combine
public void combine
Combines the state of another DoubleSummaryStatistics into this one.
Parameters:
other - another DoubleSummaryStatistics
Throws:
NullPointerException - if other 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 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:

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.
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 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 or Double.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 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 or Double.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.

Returns:
the arithmetic mean of values, or zero if none

toString
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.
Overrides:
toString in class Object
Returns:
a string representation of the object.

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