Java.Multithreading.What is the difference between submit() and execute() methods in a thread pool?

Let’s compare submit() and execute() clearly — both are used to hand over tasks to a thread pool, but they behave differently in a few key areas.

✅ 1. Return Type

Method	Returns
execute()	void
submit()	Future<?>

• submit() gives you a Future object — you can use it to:
  • Check if the task is done
  • Cancel the task
  • Get the result (or exception, if any)

✅ 2. Exception Handling

Case	execute()	submit()
Exception during execution	Thrown immediately and crashes the thread unless caught inside the Runnable	Captured inside the Future — won’t be thrown unless you call future.get()

executor.execute(() -> { throw new RuntimeException("boom"); }); // Will crash the thread

Future<?> f = executor.submit(() -> { throw new RuntimeException("boom"); });
f.get(); // Exception thrown here

✅ 3. Task Types

You want to run…	Use
Runnable	execute() or submit()
Callable<T>	submit() only

• Callable<T> returns a result or throws an exception.
• Runnable doesn’t return a result (but submit() still wraps it in a Future with null result).

✅ 4. Use Cases

• Use **execute()** when:
  • You just want to fire-and-forget a task.
  • You don’t care about the result or exceptions.
• Use **submit()** when:
  • You need to track the result, handle exceptions, or cancel the task later.

🧠 Summary

Feature	execute()	submit()
Returns value?	No	Yes — via Future
Handles exception	No (unless caught)	Yes (via Future.get())
Accepts Callable?	No	Yes