Java 8 Streams - IntStream.reduce Examples

[Last Updated: Nov 5, 2025]

Interface:

java.util.stream.IntStream

Methods:

These terminal operation performs a reduction on the elements.

int reduce(int identity,
           IntBinaryOperator op)

Parameters:

identity - the identity value for the accumulating function

op - a function for combining two values

OptionalInt reduce(IntBinaryOperator op)

Parameters:

op - a function for combining two values

Examples

package com.logicbig.example.intstream;

import java.util.stream.IntStream;

public class ReduceExample {

    public static void main(String... args) {
        IntStream intStream = IntStream.range(1, 5);
        int i = intStream.reduce(0, (a, b) -> (a + b) * 2);
        System.out.println(i);
    }
}

Output

package com.logicbig.example.intstream;

import java.util.OptionalInt;
import java.util.stream.IntStream;

public class ReduceExample2 {

    public static void main(String... args) {
        IntStream intStream = IntStream.range(1, 5);
        OptionalInt optionalInt = intStream.reduce((a, b) -> (a + b) * 2);
        if (optionalInt.isPresent()) {
            System.out.println(optionalInt.getAsInt());
        }
    }
}

Java 8 Streams - IntStream.reduce Examples

Interface:

Methods:

Examples

Output

Output

See Also