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Implementing a thread pool for batch processing

Imagine you're developing a document processing system that needs to handle multiple documents simultaneously. Each document requires intensive processing that should be done in parallel, but you want to limit the number of concurrent operations to prevent system overload. You'll implement a solution using ExecutorService to efficiently manage the processing workload.

This exercise is part of the course

Optimizing Code in Java

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Exercise instructions

  • Create a fixed thread pool, containing 3 threads.
  • Submit the processDocument(doc) method as a task to the executor.
  • Shutdown the executor without forcing termination immediately.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

public class DocumentProcessor {
    public static void main(String[] args) throws InterruptedException {
        List documents = List.of("Doc1", "Doc2", "Doc3", "Doc4", "Doc5");
        List> futures = new ArrayList<>();
        
        // Create a fixed thread pool with 3 threads
        ExecutorService executor = ____

        for (String doc : documents) {
            // Submit the processDocument() method to the executor
            futures.add(executor.submit(___));
        }
        
        // Shutdown the executor and wait for termination
        executor.____;
        executor.awaitTermination(10, TimeUnit.SECONDS);
        
        try {
            for (Future future : futures) {
                System.out.println(future.get());
            }
        } catch (ExecutionException e) {
            System.out.println("Error processing documents: " + e.getMessage());
        }
    }

    private static String processDocument(String docId) throws InterruptedException {
        System.out.println("Processing " + docId + " on thread " + Thread.currentThread().getName());
        Thread.sleep((long) (Math.random() * 1000));
        return docId + " Processed";
    }
}
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