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Java 8 Summary Statistics Example

By Arvind Rai, September 06, 2016
On this page we will provide java 8 summary statistics example. We can calculate all statistical information such as count, min, max, sum, and average in one go. Java 8 provides DoubleSummaryStatistics for double data type, IntSummaryStatistics for integer data type and LongSummaryStatistics for long data type. These classes work with stream of elements.

Summary Statistics Methods

Find the summary statistics methods. These methods belong to the java 8 classes of summary statistics.
getAverage(): It returns the average of all accepted value.
getCount(): It calculates the count of all element.
getMax(): It returns the maximum value.
getMin(): It returns the minimum value.
getSum(): It returns the sum of all elements.
accept(): It adds the element into the summary information.
combine(): It combines two summary statistics.

DoubleSummaryStatistics and Collectors.summarizingDouble()

DoubleSummaryStatistics collects the statistical information for the stream of double data type. Collectors.summarizingDouble() accepts the double mapping function and returns the Collector of double summary statistics.
DoubleSummaryStatistics dstats = list.stream()
	     .collect(Collectors.summarizingDouble(Rectangle::getWidth)); 

IntSummaryStatistics and Collectors.summarizingInt()

IntSummaryStatistics collects the statistical information for the stream of int data type. Collectors.summarizingInt() accepts the int mapping function and returns the Collector of integer summary statistics.
IntSummaryStatistics istats = list.stream()
	     .collect(Collectors.summarizingInt(Rectangle::getLength)); 

LongSummaryStatistics and Collectors.summarizingLong()

LongSummaryStatistics collects the statistical information for the stream of long data type. Collectors.summarizingLong() accepts the long mapping function and returns the Collector of long summary statistics.
LongSummaryStatistics lstats = list.stream().
	         collect(Collectors.summarizingLong(Rectangle::getId)); 

Summary Statistics Example with Primitive Data Type


SummaryStatisticsWithPrimitiveDataType.java
package com.concretepage;
import java.util.DoubleSummaryStatistics;
import java.util.IntSummaryStatistics;
import java.util.LongSummaryStatistics;
import java.util.stream.DoubleStream;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
public class SummaryStatisticsWithPrimitiveDataType {
	public static void main(String[] args) {
		System.out.println("---DoubleSummaryStatistics---");		
		DoubleSummaryStatistics dstats = DoubleStream.of(5.33d,2.34d,5.32d,2.31d,3.51d).
				collect(DoubleSummaryStatistics::new, DoubleSummaryStatistics::accept, 
						DoubleSummaryStatistics::combine);
		System.out.println("Max:"+dstats.getMax()+", Min:"+dstats.getMin());
		System.out.println("Count:"+dstats.getCount()+", Sum:"+dstats.getSum());
		System.out.println("Average:"+dstats.getAverage());		
		
		System.out.println("---LongSummaryStatistics---");			
		LongSummaryStatistics lstats = LongStream.of(51l,23l,53l,23l,35l).
				collect(LongSummaryStatistics::new, LongSummaryStatistics::accept, 
						LongSummaryStatistics::combine);
		System.out.println("Max:"+lstats.getMax()+", Min:"+lstats.getMin());
		System.out.println("Count:"+lstats.getCount()+", Sum:"+lstats.getSum());
		System.out.println("Average:"+lstats.getAverage());		
		
		System.out.println("---IntSummaryStatistics---");			
		IntSummaryStatistics istats = IntStream.of(51,22,50,27,35).
				collect(IntSummaryStatistics::new, IntSummaryStatistics::accept, 
						IntSummaryStatistics::combine);
		System.out.println("Max:"+istats.getMax()+", Min:"+istats.getMin());
		System.out.println("Count:"+istats.getCount()+", Sum:"+istats.getSum());
		System.out.println("Average:"+istats.getAverage());		
	}
} 
Output
---DoubleSummaryStatistics---
Max:5.33, Min:2.31
Count:5, Sum:18.81
Average:3.7619999999999996
---LongSummaryStatistics---
Max:53, Min:23
Count:5, Sum:185
Average:37.0
---IntSummaryStatistics---
Max:51, Min:22
Count:5, Sum:185
Average:37.0 

Summary Statistics Example with Objects


SummaryStatisticsDemoWithObject.java
package com.concretepage;
import java.util.DoubleSummaryStatistics;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.LongSummaryStatistics;
import java.util.stream.Collectors;
public class SummaryStatisticsDemoWithObject {
	public static void main(String[] args) {
		System.out.println("--DoubleSummaryStatistics--");
		List<Rectangle> list = Rectangle.getRectangle();
		DoubleSummaryStatistics dstats = list.stream()
			     .collect(Collectors.summarizingDouble(Rectangle::getWidth));
		System.out.println("Max:"+dstats.getMax()+", Min:"+dstats.getMin());
		System.out.println("Count:"+dstats.getCount()+", Sum:"+dstats.getSum());
		System.out.println("Average:"+dstats.getAverage());
		
		System.out.println("--IntSummaryStatistics--");
		list = Rectangle.getRectangle();
		IntSummaryStatistics istats = list.stream()
			     .collect(Collectors.summarizingInt(Rectangle::getLength));
		System.out.println("Max:"+istats.getMax()+", Min:"+istats.getMin());
		System.out.println("Count:"+istats.getCount()+", Sum:"+istats.getSum());
		System.out.println("Average:"+istats.getAverage());
		
		System.out.println("--LongSummaryStatistics--");
		list = Rectangle.getRectangle();
		LongSummaryStatistics lstats = list.stream().
				         collect(Collectors.summarizingLong(Rectangle::getId));
		System.out.println("Max:"+lstats.getMax()+", Min:"+lstats.getMin());
		System.out.println("Count:"+lstats.getCount()+", Sum:"+lstats.getSum());
		System.out.println("Average:"+lstats.getAverage());
	}
} 
Rectangle.java
package com.concretepage;
import java.util.ArrayList;
import java.util.List;
public class Rectangle {
	private long id;
	private int length;
	private double width;
	public Rectangle(long id, int length, double width) {
		this.id = id;
		this.length = length;
		this.width = width;
	}
	public long getId() {
		return id;
	}
	public int getLength() {
		return length;
	}
	public double getWidth() {
		return width;
	}
        public static List<Rectangle> getRectangle() {
    	    List<Rectangle> list = new ArrayList<>();
    	    list.add(new Rectangle(100l, 213, 114.23d));
    	    list.add(new Rectangle(200l, 233, 134.34d));
    	    list.add(new Rectangle(300l, 243, 144.32d));
    	    list.add(new Rectangle(400l, 253, 154.12d));
	    return list;
        }
} 
Output
--DoubleSummaryStatistics--
Max:154.12, Min:114.23
Count:4, Sum:547.01
Average:136.7525
--IntSummaryStatistics--
Max:253, Min:213
Count:4, Sum:942
Average:235.5
--LongSummaryStatistics--
Max:400, Min:100
Count:4, Sum:1000
Average:250.0 
POSTED BY
ARVIND RAI
ARVIND RAI
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