Interview Question

Runnable vs Callable?

Runnable returns no value; Callable returns a value and may throw.

💡 Concept ✅ Quick Revision ☕ Java

Answer

Runnable represents a task with no result and no declared checked exception; Callable returns a result and may throw an exception. • Runnable.run returns void. • Callable.call returns a value. • ExecutorService.submit can accept either and returns a Future.

Example

Code

java.util.concurrent.Callable<Integer> task = () -> 42;
var executor = java.util.concurrent.Executors.newSingleThreadExecutor();
System.out.println(executor.submit(task).get());
executor.shutdown();

Output

Quick Revision

Runnable returns no value; Callable returns a value and may throw.

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