java8.util

Class LongSummaryStatistics

java.lang.Object

java8.util.LongSummaryStatistics

All Implemented Interfaces:

IntConsumer, LongConsumer

public class LongSummaryStatistics
extends Object
implements LongConsumer, IntConsumer

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 longs with:

 
 LongSummaryStatistics stats = longStream.collect(LongSummaryStatistics::new,
                                                  LongSummaryStatistics::accept,
                                                  LongSummaryStatistics::combine);
 

LongSummaryStatistics can be used as a Stream.collect(Collector) reduction} target for a stream. For example:

 
 LongSummaryStatistics stats = people.stream()
                                     .collect(Collectors.summarizingLong(Person::getAge));

This computes, in a single pass, the count of people, as well as the minimum, maximum, sum, and average of their ages.

Implementation Note:
This implementation is not thread safe. However, it is safe to use Collectors.summarizingLong() 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 or the sum.

Since:

1.8

Constructor Summary

Constructors

Constructor and Description
LongSummaryStatistics() Constructs an empty instance with zero count, zero sum, Long.MAX_VALUE min, Long.MIN_VALUE max and zero average.
LongSummaryStatistics(long count, long min, long max, long sum) Constructs a non-empty instance with the specified count, min, max, and sum.

Method Summary

Modifier and Type	Method and Description
void	accept(int value) Records a new int value into the summary information.
void	accept(long value) Records a new long value into the summary information.
void	combine(LongSummaryStatistics other) Combines the state of another LongSummaryStatistics into this one.
double	getAverage() Returns the arithmetic mean of values recorded, or zero if no values have been recorded.
long	getCount() Returns the count of values recorded.
long	getMax() Returns the maximum value recorded, or Long.MIN_VALUE if no values have been recorded
long	getMin() Returns the minimum value recorded, or Long.MAX_VALUE if no values have been recorded.
long	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.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

LongSummaryStatistics

public LongSummaryStatistics()

Constructs an empty instance with zero count, zero sum, Long.MAX_VALUE min, Long.MIN_VALUE max and zero average.

LongSummaryStatistics

public LongSummaryStatistics(long count,
                             long min,
                             long max,
                             long 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

API Note:
The enforcement of argument correctness means that the retrieved set of recorded values obtained from a LongSummaryStatistics 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 - 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(int value)

Records a new int value into the summary information.

Specified by:

accept in interface IntConsumer

Parameters:

value - the input value

accept

public void accept(long value)

Records a new long value into the summary information.

Specified by:

accept in interface LongConsumer

Parameters:

value - the input value

combine

public void combine(LongSummaryStatistics other)

Combines the state of another LongSummaryStatistics into this one.

Parameters:

other - another LongSummaryStatistics

Throws:

NullPointerException - if other is null

getCount

public final long getCount()

Returns the count of values recorded.

Returns:

the count of values

getSum

public final long getSum()

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

Returns:

the sum of values, or zero if none

getMin

public final long getMin()

Returns the minimum value recorded, or Long.MAX_VALUE if no values have been recorded.

Returns:

the minimum value, or Long.MAX_VALUE if none

getMax

public final long getMax()

Returns the maximum value recorded, or Long.MIN_VALUE if no values have been recorded

Returns:

the maximum value, or Long.MIN_VALUE if none

getAverage

public final double getAverage()

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

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 this object