Thread Creation: Thread vs Runnable vs Callable<V>

1Concept

1. `Thread` class: Subclassing couples task with thread execution; 2. `Runnable`: Functional interface (`void run()`) decoupling task from thread execution; 3. `Callable<V>`: Returns a generic result (`V call()`) and can throw checked exceptions, executing inside an ExecutorService.

2Architecture Diagram

+----------------+----------------------+--------------------------+
| Mechanism      | Return Value Support | Exception Handling       |
+----------------+----------------------+--------------------------+
| Runnable       | No (void)            | Cannot throw checked     |
| Callable<V>    | Yes (returns V)      | Can throw Exception      |
+----------------+----------------------+--------------------------+

3Code Example

import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

public class ThreadCreationMasteryDemo {
    public static void main(String[] args) throws Exception {
        // Callable returning computed value
        Callable<String> dataLoader = () -> {
            Thread.sleep(50);
            return "Async Payload from Microservice";
        };

        FutureTask<String> task = new FutureTask<>(dataLoader);
        Thread workerThread = new Thread(task, "Worker-Thread-01");
        workerThread.start();

        System.out.println("Main thread continues running concurrently...");
        String result = task.get(); // Blocks until worker completes
        System.out.println("Result from worker: " + result);
    }
}

4Expected Output

Main thread continues running concurrently...
Result from worker: Async Payload from Microservice

5Key Takeaways

• ✓Always prefer implementing `Runnable` or `Callable` over extending `Thread`.
• ✓Invoking `.run()` executes synchronously on the current thread; invoke `.start()` to spawn a new OS thread.
• ✓`Callable` is designed for integration with ExecutorService and Thread Pools.