Java – How to sum all the stream integers
The sum()
method is available in the primitive int-value stream like IntStream
, not Stream<Integer>
. We can use mapToInt()
to convert a stream integers into a IntStream
.
int sum = integers.stream().mapToInt(Integer::intValue).sum();
int sum = integers.stream().mapToInt(x -> x).sum();
Full example.
Java8Stream.java
package com.mkyong.concurrency;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Stream;
public class Java8Stream {
public static void main(String[] args) {
List<Integer> integers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
int sum = integers.stream().mapToInt(Integer::intValue).sum();
System.out.println("Total : " + sum);
Stream<Integer> integers2 = Stream.iterate(1, n -> n + 1).limit(10);
IntStream intStream = integers2.mapToInt(x -> x);
int sum1 = intStream.sum();
System.out.println("Total : " + sum1);
}
}
Output
Total : 55
Total : 55
References
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