What is the difference between forEach and map in streams?

#java #java8 #stream #interview

forEach: A terminal operation that performs an action on each element of the stream but does not transform or return data.

map: An intermediate operation that transforms each element in the stream and returns a new stream of transformed elements.

Basic forEach with List

import java.util.Arrays;
import java.util.List;

public class ForEachExample {
    public static void main(String[] args) {
        List<String> names = Arrays.asList("Alice", "Bob", "Charlie");

        // Print each name using forEach
        names.forEach(name -> System.out.println(name));
    }
}

map example

List<String> names = Arrays.asList("Alice", "Bob");
names.stream().forEach(System.out::println); // Simply prints each name

List<Integer> nameLengths = names.stream()
                                 .map(String::length) // Transforms each name to its length
                                 .collect(Collectors.toList());