java8.util

Class IntSummaryStatistics

java.lang.Object

java8.util.IntSummaryStatistics

All Implemented Interfaces:

IntConsumer

public class IntSummaryStatistics
extends Object
implements 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 ints with:

 
 IntSummaryStatistics stats = intStream.collect(IntSummaryStatistics::new,
                                                IntSummaryStatistics::accept,
                                                IntSummaryStatistics::combine);
 

IntSummaryStatistics can be used as a reduction target for a stream. For example:

 
 IntSummaryStatistics stats = people.stream()
                                    .collect(Collectors.summarizingInt(Person::getDependents));

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

Implementation Note:
This implementation is not thread safe. However, it is safe to use Collectors.summarizingInt() 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
IntSummaryStatistics() Constructs an empty instance with zero count, zero sum, Integer.MAX_VALUE min, Integer.MIN_VALUE max and zero average.
IntSummaryStatistics(long count, int min, int 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 value into the summary information
void	combine(IntSummaryStatistics other) Combines the state of another IntSummaryStatistics 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.
int	getMax() Returns the maximum value recorded, or Integer.MIN_VALUE if no values have been recorded.
int	getMin() Returns the minimum value recorded, or Integer.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

IntSummaryStatistics

public IntSummaryStatistics()

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

IntSummaryStatistics

public IntSummaryStatistics(long count,
                            int min,
                            int 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 IntSummaryStatistics 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 value into the summary information

Specified by:

accept in interface IntConsumer

Parameters:

value - the input value

combine

public void combine(IntSummaryStatistics other)

Combines the state of another IntSummaryStatistics into this one.

Parameters:

other - another IntSummaryStatistics

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 int getMin()

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

Returns:

the minimum value, or Integer.MAX_VALUE if none

getMax

public final int getMax()

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

Returns:

the maximum value, or Integer.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