Example usage for java.util.stream Collectors averagingDouble

Introduction

In this page you can find the example usage for java.util.stream Collectors averagingDouble.

Prototype

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

Source Link

Document

Returns a Collector that produces the arithmetic mean of a double-valued function applied to the input elements.

Usage

From source file:Main.java

public static void main(String[] args) {
    Stream<String> s = Stream.of("1", "2", "3");

    double o = s.collect(Collectors.averagingDouble(n -> Double.parseDouble(n)));

    System.out.println(o);// ww w .ja  v  a2 s  .c o m
}

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From source file:pl.prutkowski.java.playground.java8.TestCollectors.java

/**
 * @param args the command line arguments
 *///from   w  w  w . j a v  a2s  .  c om
public static void main(String[] args) {
    Map<String, Integer> monthByLen = months.stream()
            .collect(Collectors.toMap(String::toUpperCase, m -> StringUtils.countMatches(m, "e")));

    monthByLen.forEach((month, eCount) -> System.out.println(month + " -> " + eCount));

    System.out.println("---------------------------------");

    Map<Object, List<String>> monthByLen2 = months.stream()
            .collect(Collectors.groupingBy(m -> StringUtils.countMatches(m, "e")));

    monthByLen2.forEach((count, groupedMonths) -> System.out.println(count + " -> " + groupedMonths));

    System.out.println("---------------------------------");

    Double averageLength = months.stream().collect(Collectors.averagingDouble(String::length));
    System.out.println("Average length: " + averageLength);
    System.out.println("---------------------------------");

    Double max = months.stream().collect(Collectors.summarizingDouble(String::length)).getMax();
    System.out.println("Max length: " + max);
    System.out.println("---------------------------------");

    String reduced = months.stream().collect(Collectors.reducing((m1, m2) -> (m1 + ", " + m2))).get();
    System.out.println("Reduced: " + reduced);
    System.out.println("---------------------------------");
    System.out.println(String.join(", ", months));
    System.out.println("---------------------------------");

    List<String> monthsWithZ = months.stream().filter(m -> m.contains("z")).collect(new ListCollector<>());
    System.out.println(monthsWithZ);

}

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