Java Stream reduce() Example

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

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