Java 8 Streams Java Java API
The static method, Collectors.summingLong() returns a Collector which uses a provided mapper function to convert each input element of type T to primitive long, and returns the sum of the resulting long values.
<T> Collector<T,?,Long> summingLong(ToLongFunction<? 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 SummingLongExample {
public static void main (String[] args) {
Stream<BigDecimal> s = Stream.iterate(
BigDecimal.ONE, bigDecimal ->
bigDecimal.add(BigDecimal.ONE))
.limit(10)
.peek(System.out::println);
long l = s.collect(Collectors.summingLong(
(BigDecimal::longValue)));
System.out.println("sum: " + l);
}
}
Output1
2
3
4
5
6
7
8
9
10
sum: 55
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