AtomicReference<V> is an object reference that may be updated atomically.

Examples

AtomiceReference of Double

Since there's no class like AtomicDouble, we can use AtomicReference to wrap the Double.

package com.logicbig.example;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

public class AtomicReferenceExample {
    private static AtomicReference<Double> sum = new AtomicReference<>();

    public static void main(String[] args) throws InterruptedException {
        for (int k = 0; k < 5; k++) {
            sum.set(0d);
            ExecutorService es = Executors.newFixedThreadPool(50);
            for (int i = 1; i <= 50; i++) {
                int finalI = i;
                es.execute(() -> {
                    sum.accumulateAndGet(Math.pow(1.5, finalI),
                            (d1, d2) -> d1 + d2);
                });
            }
            es.shutdown();
            es.awaitTermination(10, TimeUnit.MINUTES);
            System.out.println(sum.get());
        }
    }
}

1.9128644976421487E9
1.9128644976421487E9
1.9128644976421487E9
1.9128644976421487E9
1.9128644976421487E9

Without AtomicReference

package com.logicbig.example;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class NoAtomicReferenceExample {
    private static Double sum;

    public static void main(String[] args) throws InterruptedException {
        for (int k = 0; k < 5; k++) {
            sum=0d;
            ExecutorService es = Executors.newFixedThreadPool(50);
            for (int i = 1; i <= 50; i++) {
                int finalI = i;
                es.execute(() -> {
                    sum+=Math.pow(1.5, finalI);
                });
            }
            es.shutdown();
            es.awaitTermination(10, TimeUnit.MINUTES);
            System.out.println(sum);
        }
    }
}

1.9128638628787515E9
1.9128644976421487E9
1.9128476635299528E9
1.9128644976421487E9
1.8879854999200337E9

The result is not always same.

AtomicReference of BigDecimal

package com.logicbig.example;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;

public class AtomicReferenceExample2 {
    private static AtomicReference<BigDecimal> sum = new AtomicReference<>();

    public static void main(String[] args) throws InterruptedException {
        for (int k = 0; k < 5; k++) {
            sum.set(BigDecimal.ZERO);
            ExecutorService es = Executors.newFixedThreadPool(50);
            for (int i = 1; i <= 50; i++) {
                int finalI = i;
                es.execute(() -> {
                    sum.accumulateAndGet(new BigDecimal(1.5).pow(finalI),
                            (bg1, bg2) -> bg1.add(bg2));
                });
            }
            es.shutdown();
            es.awaitTermination(10, TimeUnit.MINUTES);
            System.out.println(sum.get().setScale(2, RoundingMode.CEILING));
        }
    }
}

1912864497.65
1912864497.65
1912864497.65
1912864497.65
1912864497.65

Example Project

Dependencies and Technologies Used:

• JDK 10
• Maven 3.3.9