In this tutorial, we will learn Java 8 Stream forEach() terminal operation with an example.

The Java Stream reduce() method is a terminal operation that can reduce all elements in the stream to a single element. 

Java Stream reduce() Example

Here is a Java Stream reduce() example:

import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args)
    {
        List<String> stringList = new ArrayList<>();

        stringList.add("one");
        stringList.add("two");
        stringList.add("three");
        stringList.add("one");

        Stream<String> stream = stringList.stream();

        Optional<String> reduced = stream.reduce((value, combinedValue) -> {
            return combinedValue + " + " + value;
        });

        System.out.println(reduced.get());
    }
}

Output:

one + three + two + one

Java Stream Methods/APIs Examples

1. Java Stream filter() Example
2. Java Stream map() Example
3. Java Stream flatMap() Example
4. Java Stream distinct() Example
5. Java Stream limit() Example
6. Java Stream peek() Example
7. Java Stream anyMatch() Example
8. Java Stream allMatch() Example
9. Java Stream noneMatch() Example
10. Java Stream collect() Example
11. Java Stream count() Example
12. Java Stream findAny() Example
13. Java Stream findFirst() Example
14. Java Stream forEach() Example
15. Java Stream min() Example
16. Java Stream max() Example
17. Java Stream reduce() Example
18. Java Stream toArray() Example