Java — Multithreading,Parallel & Asynchronous Coding in Modern Java

We’ll see how to make the use of Thread, Runnable and Executor service interface to achieve Parallel and Aync programming

public class ProductInfoService {

    public ProductInfo retrieveProductInfo(String productId) {
        delay(1000);
        return ProductInfo.builder()
                .productId(productId)
                .productOption(ProductOption.builder().productionOptionId(1).size("64GB").color("Black").price(699.99).build())
                .productOption(new ProductOption(2, "128GB", "Black", 749.99))
                .productOption(new ProductOption(3, "128GB", "Black1", 749.99))
                .productOption(new ProductOption(4, "128GB", "Black2", 749.99))
                .build();
    }
}

ReviewService.java

public class ReviewService {

    public Review retrieveReviews(String productId) {
        delay(1000);
        return Review.builder()
                .noOfReviews(200)
                .overallRating(4.5)
                .build();
    }
}

CommonUtil.java

public class CommonUtil {

    public static StopWatch stopWatch = StopWatch.create();

    public static void delay(long delayMilliSeconds) {
        try {
            sleep(delayMilliSeconds);
        } catch (Exception e) {
            LoggerUtil.log("Exception is :" + e.getMessage());
        }
    }

    public static String transForm(String s) {
        CommonUtil.delay(500);
        return s.toUpperCase();
    }

    public static void startTimer() {
        stopWatch.start();
    }

    public static void timeTaken() {
        stopWatch.stop();
        log("Total Time Taken : " + stopWatch.getTime());
    }

    public static void stopWatchReset() {
        stopWatch.reset();
    }

    public static int noOfCores() {
        return Runtime.getRuntime().availableProcessors();
    }
}

Using Runnable Interface —

ProductServiceUsingThread.java

public class ProductServiceUsingThreads {
    private ProductInfoService productInfoService;
    private ReviewService reviewService;

    public ProductServiceUsingThreads(ProductInfoService productInfoService, ReviewService reviewService) {
        this.productInfoService = productInfoService;
        this.reviewService = reviewService;
    }

    public Product retrieveProductDetails(String productId) throws InterruptedException {
        CommonUtil.stopWatch.start();

        ProductInfoServiceRunnable productInfoServiceRunnable = new ProductInfoServiceRunnable(productId);
        ReviewServiceRunnable reviewServiceRunnable = new ReviewServiceRunnable(productId);

        Thread productInfoServiceThread = new Thread(productInfoServiceRunnable);
        Thread reviewServiceThread = new Thread(reviewServiceRunnable);

        productInfoServiceThread.start();
        reviewServiceThread.start();

        productInfoServiceThread.join();
        reviewServiceThread.join();

        ProductInfo productInfo = productInfoServiceRunnable.getProductInfo();
        Review review = reviewServiceRunnable.getReview();

        CommonUtil.stopWatch.stop();
        LoggerUtil.log("Total Time Taken : "+ CommonUtil.stopWatch.getTime());
        return new Product(productId, productInfo, review);
    }

    public static void main(String[] args) throws InterruptedException {

        ProductInfoService productInfoService = new ProductInfoService();
        ReviewService reviewService = new ReviewService();
        ProductServiceUsingThreads productService = new ProductServiceUsingThreads(productInfoService, reviewService);
        String productId = "ABC123";
        Product product = productService.retrieveProductDetails(productId);
        LoggerUtil.log("Product is " + product);

    }

    /**
     * ProductInfo
     */
    private class ProductInfoServiceRunnable implements Runnable{
        private String productId;
        private ProductInfo productInfo;

        public ProductInfoServiceRunnable(String productId) {
            this.productId = productId;
        }

        @Override
        public void run() {
            // blocking call
            productInfo = productInfoService.retrieveProductInfo(productId);
        }

        public ProductInfo getProductInfo() {
            return productInfo;
        }
    }

    /**
     * Review
     */
    private class ReviewServiceRunnable implements Runnable{
        private String productId;
        @Getter
        private Review review;

        public ReviewServiceRunnable(String productId) {
            this.productId = productId;
        }

        @Override
        public void run() {
            // blocking call
            review = reviewService.retrieveReviews(productId);
        }
    }
}

Using ExecutorService Interface —

public class ProductServiceUsingExecutor {

    private static ExecutorService executorService = Executors.newFixedThreadPool(Runtime.getRuntime().availableProcessors());

    private ProductInfoService productInfoService;
    private ReviewService reviewService;

    public ProductServiceUsingExecutor(ProductInfoService productInfoService, ReviewService reviewService) {
        this.productInfoService = productInfoService;
        this.reviewService = reviewService;
    }

    public Product retrieveProductDetails(String productId) throws ExecutionException, InterruptedException {
        CommonUtil.stopWatch.start();

        Future<ProductInfo> productInfoFuture = executorService.submit(() -> productInfoService.retrieveProductInfo(productId));
        Future<Review> reviewFuture = executorService.submit(() -> reviewService.retrieveReviews(productId));

        ProductInfo productInfo = productInfoFuture.get(); // blocking call
        Review review = reviewFuture.get(); // blocking call

        CommonUtil.stopWatch.stop();
        LoggerUtil.log("Total Time Taken : " + CommonUtil.stopWatch.getTime());
        return new Product(productId, productInfo, review);
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {

        ProductInfoService productInfoService = new ProductInfoService();
        ReviewService reviewService = new ReviewService();
        ProductServiceUsingExecutor productService = new ProductServiceUsingExecutor(productInfoService, reviewService);
        String productId = "ABC123";
        Product product = productService.retrieveProductDetails(productId);
        LoggerUtil.log("Product is " + product);

        executorService.shutdown();
    }
}