Java 8 Streams Java Java API
The static method, Collectors.summingDouble() returns a Collector which uses a provided mapper function to convert each input element of type T to to primitive double, and returns the sum of the resulting double values.
<T> Collector<T,?,Double> summingDouble(ToDoubleFunction<? super T> mapper)
Examples
 package com.logicbig.example.collectors;
import java.math.BigDecimal;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class SummingDoubleExample {
public static void main (String[] args) {
Stream<BigDecimal> s = Stream.iterate(BigDecimal.ONE, bigDecimal ->
bigDecimal.add(BigDecimal.ONE))
.limit(10).peek(System.out::println);
double d = s.collect(Collectors.summingDouble(
(BigDecimal::doubleValue)));
System.out.println("sum: " + d);
}
}
Output1
2
3
4
5
6
7
8
9
10
sum: 55.0
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