Java Concurrency Interview Question: How to timeout a thread?

[@abhijitsalvi4170]

Kudos to the way the content is designed, displayed and articulately explained. Very useful for advanced developers.

[@richardashton5158]

instablaster

[@sharanyarai378]

Hit like if you need more videos on interview questions. 👍

[@propertydelver]

I've got this exact question on an interview and answered confidently: ScheduledExecutorService or CompletableFuture. I binge watched your Java Concurrency playlist the day before. Thank you so much!!

[@DefogTech]

Thats so awesome to hear! Glad these videos helped

[@rohitsharma-xt8qe]

Honestly speaking i have never seen such an awesome explanation of this topic.

[@mohammedthahajk7619]

haven't found a better concurrency tutorial on youtube till date Kudos

[@giveaway4002]

truly great. Thread.stop() got depreciated cus it can mess the program, imagine some important task is running (writing a file) in the thread and suddenly Thread.stop() is called.

[@gosnooky]

Your videos have really helped me understand Java's concurrency model. Cheers!

[@sushmithashenoy7581]

Hats off to ur efforts and elegancy. You have earned a subscriber.

[@Dawntech]

This is so useful, keep up with the good work, man :) Cheers from Brazil!

[@amanokuba4688]

Sound, Video, clarity.... all 100%

[@ArjunKumar-zu2kl]

One word for videos is just BRILLIANT.....

[@pavnn2347]

I regret that i have not seen ur videos for this long. u made hard concepts looks simple. Please do more videos if possible.

[@rohitjain1447]

Can I ask the maker of the video, where were you all these days? We missed your videos for a long period. Multithreading indeed is the very advance and necessary topic in Java. We would love to get more videos. Also if you can make videos on Design patterns, it will be great.

[@DefogTech]

Sir, I try to make 1 video per week. I have been both busy and lazy lately :) I aim to make and upload much more frequently. Next 3-4 videos are all about java concurrency interviews. Hope they will be useful. Thank you so much for the support and love shown so far!! It helps me be motivated..

[@anoop1341]

You are amazingly good man..keep the good work up. I also started recently videos for tech content and trying to be little less lazy and hope will share the url once it's enough as of now just started but your voice and clarification and design of content is awesome.

[@deepmingle]

You are certainly best of a lot when it comes to content and way of explaining. Keep it up! Git url with code would be great ! Thanks.

[@analogylibrary]

Just one word- Marvelous explanation

[@visalrao4733]

Dude..... the best explanation you can get it on youtube...Thank you so much.

[@GajendraSingh1990]

I dont think anybody can explain the java concurrency like you. Thankyou very much brother. Keep this up.

[@DefogTech]

Thank you bro!

[@drakezen]

All your videos have been top quality. Please keep up the great work!

[@ravicrazyster]

Wow. So crisp n clear

[@tusharkarkera8615]

For someone who is learning advanced java, your videos are one of the best resources I've found online. Appreciate your effort to put all these together. Can you recommend me some book(s) for mastering topics like concurrency, thread safety, writing multithreaded code, learning new java APIs, etc.?

[@DefogTech]

Concurrency in practice is a good book.. other than that personally haven't liked any..

[@manognajoshik8465]

Great!! Thanks for the valuable content you provide. Understanding multithreading has not been easy always but your videos have proven to be real blessings!! Thanks a lot sir

[@AmandeepSingh-sx9ke]

You explain so good . 😊 Thank you for your videos 🙏🏻❤️

[@dhananajaykrishna8259]

Best explanation..... Please post more of these 🙏

[@nagarajubommarapu1523]

Explained in a very very simplified way. Superb!

[@13success66]

Thanks sir sooo beautiful explanation ❣️

[@harshadakhandekar4607]

The theory is amazing yet simple. Best in KZbin. 👍 👍 👍 Saved my life :) In my recent interviews for one of the leading investment banks , they asked me several practical coding question related to the topics you covered in this playlist. Can you please make a new video on solving such coding multi threading questions.Thanks in Advance.

[@rajeevkandpal1880]

bro why you have stopped making videos. Please make videos on Java/Rx Java. you are awesome !!

[@anjalikumari2796]

Awesome explanation..Hats off to you..

[@deepakmarneni2110]

You are awesome. Your channel deserves more subscribers

[@DefogTech]

Thank you for your kind words sir!

[@apoorvanayak1736]

Great video! Suggestion for another video which is also an interview question "Implement a delayed scheduler"

[@DefogTech]

Thank you! That's a good idea

[@ahadporkar7355]

Very perspicuous and transparent ! Thank you 👍

[@rohitjain1447]

Thanks bro! Keep making , no one can explain better than you. Cheers!!

[@rishinjiya42]

Hi, your explanations are out of this world. Could you please make a video on thread-safety in static methods, please?

[@ibrahimshaikh3642]

Ur really doing great job, God bless you.

[@balak2811]

Its rather just easy to use awaitTermination for 10 mins on the the threadpool. It locks the main for 10 mins and as soon as it expires trigger the interrupts across all threads.

[@venkateshrajendran2362]

Great content and explanation. A guide to Java Async programming. What in case of CompletableFuture orTimeout(long timeout, TimeUnit unit) ( or completeOnTimeout) Will the underlying thread gets canceled?

[@abhishekjm8611]

Really amazing content. Hoping to see more.

[@vijaykumarreddyt3287]

Great tutorial, Dude

[@deepgsingh]

Very organized content, Please keep creating videos

[@justACatOnYoutube]

Upvote + 10 points for pointing a note on IO Operations case!

[@mingli9563]

Love this channel

[@MrAanjaneya]

Real interview question for me and failed miserably. Thanks for the video.

[@krishnapanigrahi6926]

Plz explain saga design pattern in microservice .Practical implementation will be much more appreciated.

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Thank you for your clear and succinct explanations. Create a book with all these topics - one per chapter. I think it will sell very well. You can use the self-service LeanPub or other online publishers to create and publish your book.

[@DefogTech]

Great suggestion! Let me think about it

[@tanveerengg]

the way of explaining concepts in step by step manner using pictorial representations and at perfect pace is commendable. This helps to absorb things for eternity. You can move (What are Java interrupts?) to this playlist and Introduction to Completable future as well so that everything is avaialable under 1 umbrella. One question, just to confirm: so in web application, in case of IO operations, it may go into thread starvation as many threads at a time in server pool will be all engaged / can get busy. However, in case of non web applications, in case of IO operation, the moment thread goes to block state, context swithing will happen and thread will be offloaded from cpu so as to server another task / thread. Because many of your videos (be it async programming or webflux) revolve around point 1 eventhough second point is also correct as explained in Spinlock. Is this correct understanding?

[@DefogTech]

Any thread which is waiting on IO does not occupy the CPU. It goes into waiting state and is offloaded from CPU. In case of web servers total thread count (say 200) limits number of simultaneous requests since even though CPU is free all 200 threads could be in waiting state. And threads are expensive (1-2 MB) so it's not wise to create too many of them.

[@tanveerengg]

@@DefogTech thanks for quick reply. How to check thread size in MBs? Also of any datastructure?

[@Nithin_Coorg]

Good Explanation! Can you make video of "Hanging Thread Detection and Handling "

[@LakshmananMe]

As always like your all other videos short, clear and easy to understand. I'm a big fan of your channel now. Hoping to learn more with your videos. Keep continuing the good work man. 😊 May I please know which tool you use to showcase the PPT? Thanks.!!!

[@DefogTech]

Thanks buddy! I use Google Slides for presentation

[@ayanSaha13291]

Thanks for content. 👍.

[@ianwanjala8621]

very helpful tutorial

[@MilanKamboya]

good stuff... really liked and explained very well...

[@amritabasu2243]

Good stuff. You dont need the keepRunning to public if you use the stop()

[@vaib5917]

More such interview questions, please. Thanks

[@ChrisAthanas]

Very well done presentation! Kudos

[@ILyaCyclone]

Perfectly explained!

[@TarekFaham]

Great video... If you use lock / unlock, how do you guarantee that the lock if acquired will be surly unlocked after say 3 seconds? This is because the caller of the class using lock/unlock may forget to unlock and in such case, we want to ensure it is going to be unlocked no matter what. How is that possible?

[@DefogTech]

AFAIK there is no such API in Java. Its upto the developer to unlock, preferably in finally blocks. FWIW, if you forget to unlock, most likely you will catch that during testing itself since no other thread will be able to acquire the lock for duration of entire run.

[@MakeItStik]

@Defog - should the easiest solution be to join the thread with timeout set as 10 min ? t.join(10*60*1000); This will make main thread wait for 10 mins and interrupt the spun thread ? Kindly correct if I am wrong or misunderstood the requirement

[@krrsss]

Great video but I don't understand one thing: if we include our steps in a while loop it will go through all steps and then check the condition and repeats this over. What if we want these steps to be different from one another and be executed only once. We cant just put them in while loop can't we?

[@DefogTech]

correct, in that case before every step we will need to add this if condition checking for volatile or interrupt..

[@AmitGadaley17]

I had the same question.

[@windowcrystal4012]

You are using while() loop & interrupt, but then you are assuming your code in run() method can come back to while() loop, but that does not always happen, right?

[@askalaveeska]

Me too have the same question. I feel that it is an invalid solution. Challenge for any thread to stop, is to abruptly leave the work/task whatever it was doing. It is not really an issue of stopping a iterative task after some iterations or just one iteration. May be shutdownhook helps?!

[@traptiagrawal1214]

Thanks for your video, how can we achieve same with threads running across various jvm?

[@developerabhishek7099]

Hey, can you tell me how to implement a case where multiple threads want to acquire a lock on an object and only the first one is allowed to process it. remaining threads which are waiting can be removed so that they can work on something else instead of waiting.

[@mahendharkhedhar7887]

Sir will you make a vedio on Netty server how it internally works please no good source is available in internet

[@Lucky-uz3je]

excellent........you are awesome.

[@prashantsharma9856]

Great Work thank you so much

[@LivenLove]

excellent explanation thanks.

[@alsto8298]

1. There is a stop method in Thread class, but it is deprecated long ago because it is unsafe for your data to stop like that and not because "threads are cooperative in nature" 2. if (booleanValue == true) --> if (booleanValue)

[@asankasiriwardena3383]

Thread class does have method called stop() that can immediately stops execution of a task, but deprecated as it is inherently unsafe

[@DefogTech]

It will start throwing exception now - bugs.openjdk.org/browse/JDK-8289610

[@AbhishekVaid]

The biggest confusion I have is how to then write the Task code in a way that we are able to check for interrupts between subsequent statements of evaluations. When we write a function, we write it imperatively, focussing on the logic that we want to implement. Putting a literal if or a global while between every statement is something I've never seen anybody coding

[@DefogTech]

In 99% of the cases you will never want to check for interrupts. It is only useful when your tasks are very long and there are reasons due to which you may want to cancel that task mid-way.

[@satyanarayanajammala5129]

awesome man... keep going

[@chandramoulisharma4188]

the way you explain this is really mind blowing. Just one question Executors.execute return the ExecutorService and Executors.submit return the Future Object, is this correct ?

[@DefogTech]

Execute method returns void, submit will return future but for callable only... Not 100 percent sure, can you please check the docs

[@kumarashutosh229]

help me understand this, `while(keepRunning == true) { ...... }`. Once you're inside the while loop, and you have got multiple steps (say readBalance(), debitAmount(), notifySuccess()), how are you expecting that the execution will halt in between these steps and read the `keepRunning` value again, unless the loop re-iterates next time(after all the 3 steps). It will be like an infinite loop, won't it? Since, the while loop condition is checked at the `beginning of each iteration`, the loop will `continue to execute` the current iteration even after `keepRunning` becomes false. It will stop ONLLY at the beginning of the next iteration when the condition `(keepRunning == true)` is false. Correct me if I'm wrong here :) Thanks for the video!

[@diegoramos27]

10:23, is the task required to check on isInterrupted for this implementation to work ? Or can I simply rely on future.get Timeout to be sure that the task will be cancelled if the time out has exceeded?

[@youngsambyun5854]

thank you for this video very good !!!

[@ratneshchouhan6]

@Defog, how to handle deadlock situation and how to resolve it?

[@DefogTech]

Simplest way is to acquire the locks in same order in all threads, that would avoid locks. If locks are based on objects then get hashCode of object, sort based on that hashCode, then acquire locks in that order.

[@MakeItStik]

Avoid circular wait (i.e acquiring lock ) and to break circular wait you acquire locks in all threads in same sequence. T1 - lockA --> lockB T2 - lockA --> lockB

[@aakash24041990]

@Defog Tech : Please create videos on java collections.

[@kengerfil]

Wait, I'm consufed: on 01:03 you were saying there's no API to stop a Thread, while on 09:26 you are calling "stop()" method of the Thread class. So, is there API to stop or not?

[@ramanapanku4306]

Very knowledgeable

[@ashitateotia8101]

Can you please explain why while timeout we are using stop() method when this method is not supported anymore.

[@logicbuffer2162]

Great video.

[@dnbhatia85]

Super explained

[@gopikumar857]

bro.. could you do a video on Big 0 notation?

[@aleksandarvanced5434]

Make more videos like this!

[@shivendratiwari3238]

Bro why don't you create a playlist which dives deep in stream exploring all the APIs

[@zss123456789]

Thank you so much!

[@chandra111443]

Nice explanation

[@shalingupta8281]

Can you make a video on Static and non-static synchronization, I have been asked this question many times and recruiter never seems to be happy.

[@DefogTech]

Can you elaborate more on the question?

[@nikkisingh1041]

how can i create a runtime class and mapped it with hibernate without adding and restarting our application please make a video on it.

[@prathameshchaudhari1306]

Need one help in one scenario. I am creating a new thread which does recursive task. After some time thread gives stack over flow error. I want to run recursive task with out giving stack overflow error. How to do it?

[@DefogTech]

Issue is not thread related, it is about number of times the recursive task being called. Put a counter and see what the count is and when program stops printing it.

[@MakeItStik]

StackOverflow in a recursion occurs if your exit condition is not met in any of the iterations. Exit condition helps your stack to collapse back to initial state. Try creating Euler diagram for few iterations.

[@bigheat86]

Danke!

[@SurendraBabuK]

Which logic will be there in task.stop() ?

[@slr150]

What happens when your task calls a library that swallows the InterruptedException (I've seen this in certain JDBC drivers)? .

[@DefogTech]

That's IO operation, most java IO librarues respect the interrupts but yes, it's upto the library code to handle it.

[@081sidd]

So, does it mean that we can never guarantee to stop/cancel a thread at a given point of time? Please correct if I have got it all wrong

[@DefogTech]

yes, thats correct..

[@windowcrystal4012]

1:05 you said there is not stop() method to stop the thread. But as far as I know, there is indeed a stop() but just deprecated.

[@NathanJohnson815]

It's deprecated, meaning you shouldn't use it. And anyone reviewing your code in either an interview or real life would hopefully not let you use it ;)

[@babasahebgongale5006]

Super!

[@aurojitbasak3249]

Please share more interview questions

[@maverick_entertainment21]

Amazing

[@ironhide9955]

there is stop() in Thread class but its deprecated, but that would be a very simple solution.

[@DefogTech]

It was removed purposely since if you stop the thread, the objects it was mutating can be in bad state.. since only that thread knows what should be the right state of the object, it should be allowed to change object state properly and only then stop

[@chetanbhandari3033]

Bro thnx lot

[@Existentialkev]

Why would you use thread.sleep() for time out logic?? that would suspend the execution of the thread right? What the question wants is for you to ask the thread to stop *after* 10 minutes has elapsed which you demonstrated with the ExecutorService and Future.

[@DefogTech]

Right, sleep() will suspend execution of current thread but the Runnable/task being executed in new thread or ExecutorService will continue to run

[@Existentialkev]

@@DefogTech I see so the idea is for the suspended thread to check the result of another thread that is actually doing the task in the runnable after a set amount of time? And if the task isn't complete call interrupt () ?

[@DefogTech]

Exactly! Also yours is also a good point.. a simpler way could be for the task itself to note start time and every once in a while check if it's over deadline.. if so just return...

[@diegoramos27]

Is there any way to timeout the HttpRequest after a specified time ? I tried both Connection_Timeout and Read_Timeout ? thanks

[@DefogTech]

Yes, I haven't used core API for Http connection but libraries like Retrofit and Spring http client both allow you to set timeouts

[@shankarm2848]

Is there any way to kill a interrupted thread without using while loop?

[@DefogTech]

nope, threads are cooperative in Java, cant kill them.