CODEWITHSUNDEEP
javajava-stream
Won Hee Lee
Won Hee Lee

Reputation: 65

How to use Intstream and map method

I have solved the problems from the Java book, and I have some questions.

In the code below, I want to create a new stream by doubling each element using the map intermediate operation. And I want to print a new stream to get the sum of all the elements except the number less than 50 in the generated stream.

How can i solve this ??

    package test;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;
import java.util.Optional;
import java.util.stream.IntStream;

public class tt {


public static void main(String[] args) {
    try {
        Stream <String> lines = Files.lines(Paths.get("C:\\Users\\wonheelee\\eclipse-workspace\\test\\stream-data.txt"));


        IntStream IS = lines.mapToInt(Integer::valueOf);

        IS.forEach(System.out::println);
        lines.close();

    } catch (IOException e) {
       // No action 
    }
}
}

Upvotes: 0

Views: 593

Answers (1)

Thiyagu
Thiyagu

Reputation: 17890

Here you go..

int result = lines
            .mapToInt(Integer::parseInt)
            .map(element -> element * 2) //Double
            .filter(element -> element >= 50) //Filter out values less than 50
            .sum(); //sum

You can combine the mapToInt and map in one mapToInt itself 

.mapToInt(element -> Integer.parseInt(element) * 2)

Also, note as Aomine@ mentioned in the comments, using Integer.parseInt to avoid an extra boxing/unboxing.

I'm not quite sure what you mean by create a new stream. You can get a new Stream by calling Files.lines again.

You cannot reuse a Stream once it is already consumed.

Reference:

Is there any way to reuse a Stream?

Upvotes: 2

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