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Java 8 Streams - IntStream.collect Examples

[Last Updated: Nov 8, 2025]

Java 8 Streams Java Java API 

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Interface:

java.util.stream.IntStream

java.lang.AutoCloseableAutoCloseablejava.util.stream.BaseStreamBaseStreamjava.util.stream.IntStreamIntStreamLogicBig

Method:

<R> R collect(Supplier<R> supplier,
              ObjIntConsumer<R> accumulator,
              BiConsumer<R,R> combiner)

This method performs a mutable reduction operation on the elements of this stream.

Type Parameter:
R - type of the result
Parameters:
supplier - a function that creates a new result container (mutable object) . For a parallel execution, this function may be called multiple times. It must return a fresh value each time.
accumulator - a function for incorporating an additional element into a result.
combiner - a function for combining two values, used in parallel stream, combines the results received from different threads.

Examples


package com.logicbig.example.intstream;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.IntStream;

public class CollectExample {

    public static void main(String... args) {
        IntStream intStream = IntStream.range(1, 10000);
        AtomicInteger ai = intStream.filter(i -> i % 2 == 0)
                                    .parallel()
                                    .collect(AtomicInteger::new,
                                            (a, b) -> a.set(a.get() + b),
                                            (a, b) -> a.set(a.get() + b.get())
                                    );
        System.out.println(ai);
    }
}

Output

24995000

See Also