Top V Departure Betwixt Callable Together With Runnable Interface Inward Java

The departure betwixt Callable together with Runnable is i of the most often asked multi-threading together with concurrency interview inquiry inwards Java world. I remember, it was 2007 when I firstly heard nearly Callable interface together with that also on a telephonic interview. Till then, I was happy using Runnable to implement threads together with but started paying attending to Java 1.5, equally most of the application past times thence using Java 1.4. That i interview inquiry encouraged me to larn to a greater extent than nearly several other useful features introduced inwards Java v concurrency library e.g. CountDownLatch, CyclicBarrier, Semaphore, Atomic variables, together with Thread pool. This is i of the reasons I ever encourage Java developer to give/take regular interviews, but to update your knowledge.

In this article, I'll hash out how to reply this inquiry past times highlighting approximately cardinal differences betwixt Runnable together with Callable inwards Java. I didn't know all these points at that fourth dimension but my inquiry after that helped to larn to a greater extent than nearly the Callable interface.


Even though both Callable together with Runnable interface are used to encapsulate chore supposed to hold out executed past times approximately other thread, in that place is 2 cardinal departure betwixt Callable together with Runnable interface:

1. Callable tin laissez passer on notice render result
2. Callable tin laissez passer on notice throw checked Exception.

In fact, Callable interface was introduced inwards Java 1.5 to address the higher upwards 2 limitations of Runnable interface i.e. Runnable cannot render the lawsuit of computation which is essential if you lot are performing approximately computing chore inwards approximately other thread together with Runnable cannot throw checked exception. Now, Java's multi-threading API has got best of both worlds. You tin laissez passer on notice farther read Core Java Volume 1 - Fundamentals by Cay S. Horstmann to larn to a greater extent than nearly when to purpose Runnable vs Callable piece coding multi-threaded Java applications.

As I said, what is the departure betwixt Callable together with Runnable is also i of the often asked multithreading interview questions inwards Java, thence knowing the departure non entirely aid you lot to write improve code but also to attain good on interviews? Let's run into a duo of to a greater extent than differences betwixt these 2 interfaces to empathise them better.

Runnable vs Callable

Before looking at the departure betwixt the Runnable together with Callable interface, let's await at the similarities betwixt them, they are indeed quite similar.

1) The most mutual matter betwixt them is that both are used to encapsulate code which needs to hold out run inwards parallel on a split upwards thread.

2) The 2nd similarity betwixt them is that bot tin laissez passer on notice hold out used amongst Executors framework introduced inwards Java 5. Executors framework defines ExecutorService interface which tin laissez passer on notice convey together with execute Runnable together with Callable.

3) You tin laissez passer on notice also convert Runnable to Callable past times using the next utility method provided past times Executors class

As I said, both are used to encapsulate the code, you lot desire to run inwards a split upwards thread, but in that place is a limitation, you lot cannot execute Callable instance inwards a thread, but similar you lot execute a Runnable instance, you lot demand an ExecutorService instance. Let's run into them inwards detail.

Callable callable = Executors.callable(Runnable task);

4) The quaternary similarity betwixt Runnable together with Callable interface is that both are SAM type i.e. they guide maintain a unmarried abstract method, which agency they tin laissez passer on notice hold out used in lambda appear inwards Java 8 as shown below.

new Thread( () -> System.out.println("Runnable") ).start()

Now, nosotros know the similarities betwixt Runnable together with Callable interface, it's fourth dimension to run into the differences again. On the same note, you lot tin laissez passer on notice also purpose the Java Programming Interview exposed mass to cheque out similar questions for to a greater extent than practice.

Difference betwixt Runnable vs Callable interface

Here are approximately of import departure betwixt these 2 cardinal interfaces of Java's multithreading API inwards the betoken format.


1) Existence together with Availability
First together with most of import departure betwixt Runnable together with Callable interface is that Runnable is available inwards Java correct from the starting fourth dimension i.e. JDK 1.0 piece Callable was later on added to Java 5, thence you lot cannot purpose Callable earlier Java 5.


2) Result
The 2nd cardinal departure betwixt Callable together with Runnable is that Callable tin laissez passer on notice render the lawsuit of parallel processing of a task. It returns a Future object, which represents the lifecycle of a chore together with provides methods to cheque if the chore has been completed or canceled, retrieve the lawsuit or cancel the task. Since render type of Runnable's run() method is void, it cannot render anything.


3) Checked Exception
Another worth noting departure betwixt these 2 interfaces is that Callable's call() method tin laissez passer on notice throw Checked exception piece Runnable's run() method cannot throw checked exception.


4) The call() vs run() methods
In club to purpose Callable, you lot demand to override the call() method piece inwards club to purpose Runnable interface you lot demand to override the run() method inwards Java.


5) Execution
There is i limitation piece using Callable interface inwards Java that you lot cannot overstep it to Thread equally you lot overstep the Runnable instance. There is no constructor defined inwards the Thread flat which accepts a Callable interface. So inwards club to execute a Callable illustration you lot demand to purpose the ExecutorService interface of Java v Executor framework. This interface defines submit() method which accepts a Callable illustration together with render a Future object which holds the lawsuit of computation equally shown below:

Future lawsuit = exec.submit(aCallable); lawsuit = holder.get();

Remember, Future.get() is a blocking method together with blocks until execution is finished, thence you lot should ever telephone phone this method amongst a timeout to avoid deadlock or livelock inwards your application.


In short, hither is the cardinal departure betwixt Runnable together with Callable inwards Java:

That's all nearly the difference betwixt a Callable together with Runnable interface inwards Java. Apart from the basic fact that Callable was added later on inwards Java 5, you lot should recollect that Callable tin laissez passer on notice render lawsuit together with throw checked exception but you lot demand ExecutorService to execute Callable instance. Good matter is that both Runnable together with Callable are SAM type thence you lot tin laissez passer on notice purpose them inwards lambda expressions.


Similar frequently asked thread interview questions you lot may like

• Difference betwixt start() together with run() method inwards Java? (answer)
• Difference betwixt execute() together with submit() method of Executor inwards Java? (answer)
• How to bring together multiple threads inwards Java? (answer)
• How to halt a thread inwards Java? (answer)
• How to solve producer consumer occupation using blocking queue inwards Java? (solution)
• Top l Thread Interview Questions for experienced programmers (list)

Further Learning
Multithreading together with Parallel Computing inwards Java
Java Concurrency inwards Practice - The Book
Applying Concurrency together with Multi-threading to Common Java Patterns
Java Concurrency inwards Practice Course past times Heinz Kabutz

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