Class 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 sum.

Since:
1.8

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.

Methods

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.
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 declared in class java.lang.Object

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

Methods declared in interface java.util.function.IntConsumer

andThen

Methods declared in interface java.util.function.LongConsumer

andThen

Constructors

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

Methods

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 the object.

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/LongSummaryStatistics.html