Java Streams - Stream mapToLong(ToLongFunction mapper) example

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Stream mapToLong(ToLongFunction<? super T> mapper) returns a LongStream by applying the function to the stream.

Syntax

mapToLong has the following syntax.

LongStream mapToLong(ToLongFunction<? super T> mapper)

Example

The following example shows how to use mapToLong.

import java.util.Arrays;
import java.util.List;
//from w w w.  j  a  va2  s. c o m
public class Main {
  public static void main(String[] args) {
    List<String> stringList = Arrays.asList("1","2","3","4","5");

    stringList.stream()
           .mapToLong(n-> Long.parseLong(n) )
           .filter(n-> n%2 == 0)
           .forEach(System.out::println);
  }
}

The code above generates the following result.

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