Class LongSummaryStatistics

java.lang.Object

java.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 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	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	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.
final double	getAverage()	Returns the arithmetic mean of values recorded, or zero if no values have been recorded.
final long	getCount()	Returns the count of values recorded.
final long	getMax()	Returns the maximum value recorded, or Long.MIN_VALUE if no values have been recorded
final long	getMin()	Returns the minimum value recorded, or Long.MAX_VALUE if no values have been recorded.
final 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 declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Answers a new instance of the same class as the receiver, whose slots have been filled in with the values in the slots of the receiver.
boolean	equals(Object o)	Compares the argument to the receiver, and answers true if they represent the same object using a class specific comparison.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. May cause performance issues, deadlocks and hangs.
final Class<? extends Object>	getClass()	Answers the unique instance of java.lang.Class which represents the class of the receiver.
int	hashCode()	Answers an integer hash code for the receiver.
final void	notify()	Causes one thread which is waiting on the receiver to be made ready to run.
final void	notifyAll()	Causes all threads which are waiting on the receiver to be made ready to run.
final void	wait()	Causes the thread which sent this message to be made not ready to run pending some change in the receiver (as indicated by notify or notifyAll).
final void	wait(long time)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.
final void	wait(long time, int frac)	Causes the thread which sent this message to be made not ready to run either pending some change in the receiver (as indicated by notify or notifyAll) or the expiration of the timeout.

Methods declared in interface IntConsumer

andThen

Modifier and Type	Method	Description
default IntConsumer	andThen(IntConsumer after)	Returns a composed IntConsumer that performs, in sequence, this operation followed by the after operation.

Methods declared in interface LongConsumer

andThen

Modifier and Type	Method	Description
default LongConsumer	andThen(LongConsumer after)	Returns a composed LongConsumer that performs, in sequence, this operation followed by the after operation.

Constructor Details

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 Details

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:

String a printable representation for the receiver.