Collectors averagingDouble() method in Java 8

The averagingDouble() method of the Collectors class in Java 8 returns a Collector that is the arithmetic mean of a double-valued function applied to the input elements.

The syntax is as follows −

public static <T> Collector<T,?,Double> averagingDouble(ToDoubleFunction<? super T> mapper)

Here, the parameters −

• T − Type of the input elements

• mapper − Function extracting the property to be summed

• Double − It wraps a value of the primitive type double in an object.

• ToDoubleFunction − - A function that produces a double-valued result.

To work with Collectors class in Java, import the following package −

import java.util.stream.Collectors;

The following is an example to implement averagingDouble() method in Java −

Example

 Live Demo

import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Demo {
   public static void main(String[] args) {
      Stream<String> stream = Stream.of("20", "50", "75", "100", "150", "200");
      double res = stream.collect(Collectors.averagingDouble(a -> Double.parseDouble(a)));
      System.out.println("Arithmetic Mean of the stream elements = "+res);
   }
}

Output

Arithmetic Mean of the stream elements = 99.16666666666667