What is the difference between Callable and Runnable in Java?

What is the difference between Callable and Runnable in Java?

Callable and Runnable are both interfaces in Java used for concurrent programming. The main difference is that Callable can return a result and can throw checked exceptions, while Runnable cannot return a result and cannot throw checked exceptions.

Can you give an example of how to use both?

Sure! Here's a simple example:

For Runnable:

Runnable task = () -> {
    System.out.println("Running a Runnable task.");
};
new Thread(task).start();

For Callable:

Callable<Integer> task = () -> {
    return 42;
};
ExecutorService executor = Executors.newSingleThreadExecutor();
Future<Integer> future = executor.submit(task);
System.out.println("Callable result: " + future.get());
executor.shutdown();

What happens if I try to use Callable without handling exceptions?

If you use Callable and don't handle exceptions, it will throw a checked exception at runtime, which must be caught or declared in the method signature. This is different from Runnable, which does not throw checked exceptions.

Which one should I use in my project?

It depends on your needs. Use Runnable if you don't need a return value or exception handling. Use Callable if you need to return a result or handle exceptions.