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Java compact1, compact2, compact3 java.util Class LongSummaryStatistics（JDK8）

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Java™ Platform
Standard Ed. 8
compact1, compact2, compact3
java.util

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 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.toLongStatistics() 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

    • Constructor Summary

      Constructors 
      Constructor and Description
      LongSummaryStatistics()
      Construct an empty instance with zero count, zero sum, Long.MAX_VALUE min, Long.MIN_VALUE max and zero average.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      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 string representation of the object.

    • Constructor Detail

      • LongSummaryStatistics

        public LongSummaryStatistics()
        Construct an empty instance with zero count, zero sum, Long.MAX_VALUE min, Long.MIN_VALUE max and zero average.

    • 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()
        Description copied from class: Object
        Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

        The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

         getClass().getName() + '@' + Integer.toHexString(hashCode())
        Overrides:
        toString in class Object
        Returns:
        a string representation of the object.
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Java™ Platform
Standard Ed. 8

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