Java collections framework interview questions and Answers | MOST ASKED | Core Java | Code Decode

This video contains tricky Java Collections Interview Questions and Answers for Freshers as well as for Experience Candidates. It also contains Internal Working of Hashmap
Collections Interview Questions part -2 : • Most Asked Java Collec...
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Collection Hierarchy 00:16
Map doesn’t extend the Collection Interface 13:13
Difference between fail-fast and fail-safe Iterators 14:51
java BlockingQueue 16:43
Difference between Synchronized Collection and Concurrent Collection with pictorial understanding 18: 10
Internal Working of hash map with pictorial explanation 20:13
In this video of java collections interview questions we have covered java collection framework interview questions or top collections interview questions starting with hierarchy of collection framework in java
collection hierarchy in java will demonstrate in depth knowledge of candidate.
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In java collections interview questions. java.util.Collection is the root
of the Java Collection framework and most of the collections in Java are inherited from this interface except Map Interface
java.util.List :
Contains ordered elements
May include duplicates
Supports the index-based search, random access but elements can be easily inserted irrespective of the position.
java.util.Queue
follows a FIFO approach
Elements adds at rear end and removes from the front end.
java.util.Set:
Doesn’t define an order for the elements hence index-based search is not supported
Doesn’t contain duplicates
java.util.Map
Represents a key, value pair
Map interface does not implement the Collection.
It can only contain a unique key
can have duplicate values
In java collections interview questions Similarly all these interfaces have implementing class and all those implementing classes have some 2 3 unique feature which differentiate them from the other collections. Please have a look at each of them in video as i have limited word limit here :)
The Java BlockingQueue interface, java.util.concurrent.BlockingQueue, represents a queue which is thread safe to put elements into, and take elements out of from. In other words, multiple threads can be inserting and taking elements concurrently from a Java BlockingQueue, without any concurrency issues arising.
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[@shubhamtagalpallewar7125]

It helped me in my interview preparation.. thanks

[@CodeDecode]

Hope you get all your interviews cleared. All the the best 🤟

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[@kirushnashirre6791]

Though I knew about the framework completely, I had an issue explaining it in an organized way, you are just awesome!

[@CodeDecode]

Thanks 👍

[@rohanbhargava3953]

Great video! One addition to the last question on implementation of HashMap Since Java 8, once a threshold limit is reached for the number of linked list elements added at a particular node, the linked list is re-ordered to a binary tree to implement faster search for collision cases.

[@CodeDecode]

Thanks for the info

[@JenilCalcuttawala]

Binary but Binary Search Tree right?

[@JustOssetian]

​@@JenilCalcuttawala red black tree

[@coincidentIndia]

SortedSet uses Comparator(Comparator

[@SuperMilanjain]

Really a nice approach to make understand the topic. Just one request, plz add some behavioral questions related to collection as interviewer can ask that also.

[@jasper5016]

It enhanced my knowledge for sure. Thanks.

[@Athira_Surendran]

The way you explaining each topic is awesome. Thank you for the amazing video.

[@CodeDecode]

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[@anuradhap4055]

Hi.. Your videos are the best. You explain so well. Thanks a ton for your efforts. One request.. can you please make a video on how time complexity works in collection?. It would be a great help. Thanks in advance. 🙂

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[@CodeDecode]

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[@sharathrajesh9494]

Hi Mam, this video about collections helped me during my interview with TCS and I secured a job offer! Thank you very much and I will continue to look through your other videos to help broaden my knowledge

[@prakashkaruppusamy3817]

This is a awesome 'Ready Reckoner'. I watched this and all are explained clear and to the point. This is great effort by the creator. Please make more topics and please make more videos. I totally understood the points. All the very best team 👍👏 With Regards, Prakash Karuppusamy

[@CodeDecode]

Thanks for the nice words Prakash. We will sure make more videos like this ....

[@shivaniagrawal4473]

Thank u so much,your way of explaining concepts are wonderful.I am feeling so confident in Java after watching your interview questions.

[@CodeDecode]

Thanks Shivani 👍👍. Keep learning keep shining ⭐✨⭐✨

[@nikhleshagrawal]

from Java 8, the linked lists are dynamically replaced with balanced binary search trees in collision resolution after the number of collisions in a given bucket location exceed a certain threshold. This change offers a performance boost, since, in the case of a collision, storage and retrieval happen in O(log n).

[@CodeDecode]

Yes we have covered that in latest videos I. E. top interview questions 👍👍. Thanks

[@jakubdudek4133]

For others who are interested in that particular topic, the threshold by default is 8 as far as I remember. :) So "after" 8 nodes, LinkedList is being switched to Tree Balance Structure.

[@robinbhargava111]

Very informative and quick to brush up collection framework with examples.

[@CodeDecode]

Thanks Robin 🙂👍

[@savitarohra3905]

Everything explained to the point!! Thank you for making great videos

[@CodeDecode]

Thanks Savita 👍

[@mitra.1]

Thanks a lot.. The best Collection summary available on YT.

[@pallavipatare2004]

This is my first ever KZbin comment. I just logged in to youtube so that I can comment on your video. You are awesome. Very well explained, very well organised. Keep it up. No nonsense videos. I am preparing for my interviews using your videos only. Pls countinue uploading many such videos.

[@CodeDecode]

Thanks Pallavi 🙂👍

[@GaneshSingh1]

I have read theory before but confused after this video cleared all doubts about Hashmap,, thanks a lot

[@CodeDecode]

We are glad to know that this helps Ganesh 🙏👍

[@robelhailab394]

You are awesome, thanks for thanking your time to help us on interview preparations!

[@CodeDecode]

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[@robelhailab394]

Great Explanation!!! One more point: Hashtable doesn’t extend Hashmap. It extends Dictionary Class.

[@CodeDecode]

👍👍

[@dasarajusaikumar8585]

your phone vibrates in almost all of your videos. thats very nice :-). it's not a complaint, take it as a compliment

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[@RickyYadav_at_googleplus]

very nicely explained... eagerly waiting for Multi-threading concepts.. once again good job!

[@CodeDecode]

Thanks .......

[@praveenpatel3957]

This special video covered all related to collection and its interview questions have watched so many videos about that but here have learnt in very different way thanks for sharing such valuable content in the video keep sharing like this we get to learn more..❤❤

[@venkatv3690]

Best i have seen before the way ur explaining very well thank you

[@CodeDecode]

you're welcome venkat

[@deviprasadhota2617]

Nice work...one mistake is map interface doesnt extends(not implement) Collection interface

[@nagavenkatakishore4109]

Nice explanation friend thank you very much for sharing.

[@CodeDecode]

Thanks for the nice words 👍

[@farrukhahmedsid]

Yes this is literally most asked and top questions. Thanks.

[@CodeDecode]

Thanks

[@vinodkumar-lq7oo]

Really very good explanation. We are lucky to watch this.

[@CodeDecode]

Thanks Vinod 👍

[@sureshgarine]

Thank you so much, madam. You explained in-depth and very nicely

[@CodeDecode]

Thanks 👍👍

[@kajalkukreja694]

Very good questions and their detailed explanation. Thanks 👍👍

[@CodeDecode]

Thanks for the nice words...

[@rishiraj2548]

5 lakh 48 thousand + views Congrats 🎉🎉🎉

[@CodeDecode]

Thanks Rishi for your constant support

[@satishdhaigude629]

Thank you, nice explanation of all collections, mostly I like internal working of hash map, got the more clarity….

[@CodeDecode]

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[@parulanand7902]

Thank you for the amazing video.. It helped me a lot for my interview.

[@CodeDecode]

Thanks for writing back to us Parul . We hope u land at your dream job soon. All the very best from team code decode, for your interviews. Keep learning keep growing.

[@solomonrajkumar5537]

Hats off very nicely explained and your presentation is also too good.

[@CodeDecode]

Thanks 👍

[@sanjeetkrsinha]

Your video helps me a lot for preparation of interview. Do you have any the text tutorial also for it?

[@kp-ps7wi]

Explanation is awesome. Just a suggestion. In the diagram just put dotted line for interface and solid line for class. So while seeing the diagram people will understand the concept.

[@CodeDecode]

That's a very nice suggestion. Thanks 🙏👍👍👍👍

[@sreejak6776]

Pleasr create more tricky questions on collections

[@CodeDecode]

sure sreeja we will create soon

[@gurudassulebhavikar]

In case of hash collision it also uses equals method to check if key is same. If it is same then it updates the value. Otherwise, new node is inserted.

[@AK-tt7fc]

the video is very usefull . at 3.40 you interchangeably used implements and extends keyword . if possible correct that .

[@kaushikigoel759]

Each and every video is so informative!! Love your content ❤️..

[@CodeDecode]

thanks kaushiki

[@vinayvjs628]

Best study video for interview

[@CodeDecode]

Thanks 👍👍

[@anshumanpanigrahi7817]

Ma'am, thank you for this. It really helped me in cracking Amdocs. I was able to recall the exact same thing you taught in this video. I can say, that I've done DSA and used every framework that's why it looked very understandable at the very first go.

[@CodeDecode]

Congratulations Anshuman 🎊🎊🎉🎉

[@shouryapradhan184]

HI Anshuman , Bro i have an Amdocs interview in upcomming week. Can u pls help me in that like how is the interview and what questions were asked in that interview please ? Can we connect?

[@anshumanpanigrahi7817]

@@shouryapradhan184 Topics- Java, Oops, Threads, Collections, SQL, DBMS, Unix commands, 2 programming questions. Go through interview experiences from gfg & Coding Ninjas/CodeStudio, that'll be enough. Mine was for developer profile.

[@shouryapradhan184]

@@anshumanpanigrahi7817 Thanks a lot for reply bro. Mine interview is also for developer role 2 years of experience. May i know what type of programming questions were asked in interview ?

[@krishteja2959]

superb.....Nice presentation .If possible, can you please do video like most asked interview questions which covers all the concepts in core and advanced

[@CodeDecode]

Sure I will cover all of them, from simple to advanced in parts soon

[@BhushanRawoolShridhar]

Nice explanation,you are doing a great job. Thank You

[@CodeDecode]

Thanks Bhushan 👍👍

[@Hare_Krishna143]

Such helpful content and appreciate your hardwork Thank you mam!!

[@CodeDecode]

Thanks Manoj 🙂👍

[@sneharaghuwanshi4933]

Hello Ma'am, I have learnt a lot from your channel thank you so much. I have one doubt here that the linked list does not support index based search but it has a get method through which the element is at a specific position?

[@vipinyadav7921]

Very nicely explained, Please make a video on whole springboot concepts... With theory and coding as well

[@CodeDecode]

Sure will make a video on that too

[@shubhammowade.6019]

Respect for your explanation ma'am...

[@CodeDecode]

Thanks 👍

[@seethegodinyou]

Thank you so much , I found all my interviews questions from there...We need people like you!

[@CodeDecode]

Thanks for nice words chandan

[@kazaasekhar]

very nice but need more questions from collections with demonistration

[@CodeDecode]

Sure we will create soon

[@bhavyabhardwaj4563]

Very good explanation of Internal working of hashmap. Liked it.

[@CodeDecode]

Thanks

[@chishamalama]

Thank you once again for explaiing clearly

[@CodeDecode]

Thanks Chisha Malama 🙂🙂👍👍

[@croydon21H]

Good videos. Question - how can a programmer know, if there was a hashmap collision or not?

[@dineshsolanki1666]

an image with all the information would be great

[@shubhamshende9995]

very clear and crisp explaination 💥

[@CodeDecode]

Thanks Shubham 🙂👍

[@rishiraj2548]

16:07 ConcurrentModificationException:- When modification is performed on a collection by the same thread which is iterating over that collection. It's not about two distinct threads for iterating and modifying.

[@kemparaj565]

Very good. Explanation. Thank You 😊

[@CodeDecode]

Thanks 🙏

[@kamallochannayak2706]

Thank you mam .....your way of talking/understanding.....love it

[@CodeDecode]

You're welcome kamal.....

[@kamallochannayak2706]

❤

[@jeevansaimanikanta782]

Thanks . Please do the video showing the internal implementation of HashSet as well and also tell the info like in which scenario which kind of Collection is the suitable one to use

[@CodeDecode]

Nice topic thanks 👍

[@nidhi10sharma]

Excellent videos, Thank you so much!

[@CodeDecode]

Thanks Nidhi 🙂👍

[@amitarcade]

For hashmap internal working, hashcode method is called by hash method of HashMap and hash method calculates index based on hashcode value

[@CodeDecode]

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[@sagarmane3291]

Superbbb...! your explanation skills are just awesome.... and ur voice is adorable as well. thanks for this questions set it will be really helpful

[@CodeDecode]

Thanks Sagar 🙂🙂

[@venkatkancharla984]

thanks for all the tricky quaetions, please explain the HashMap with some examples and this is very short. because i was understanding this only theoretically but havent't implemented. bit more explanation on hash map.. it also talks about the equals() and hashCode() contract..

[@CodeDecode]

Hi Venkat These are only interview questions. Will create tutorial for this very soon 👍👍

[@venkatkancharla984]

@@CodeDecode sure, thanks

[@RaviK-lv9zf]

Beautiful voice.. 😅 and the content is so good that you almost covered main topics that can consume most of the time at institutes.

[@CodeDecode]

Thanks Ravi 🙂🙂

[@harshadakankhar4875]

Please make a video for Spring interview questions as well..

[@CodeDecode]

Sure will do that soon

[@harshadakankhar4875]

Code Decode anyway the way you explain is just wow 🤗🤗

[@CodeDecode]

thanks :) 👍

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Very clear explanation.. and provide example code 👍👍👍👍

[@CodeDecode]

Thanks Siva 👍👍

[@PKS-ky9se]

Thanks for the great video. Helped me a lot.

[@CodeDecode]

You're welcome

[@sriharini8309]

Very nice one. CAN you also please elaborate on live examples on each collection class. That's wud help us a lot

[@CodeDecode]

Sure Anupama 👍👍

[@sriharini8309]

@@CodeDecode Thaks much for the reply. Please make a video on recat and angula part also.

[@sushmakolli1119]

Please make another video(part2)on collections tricky questions and include concepts like internal working of hash set

[@CodeDecode]

kzbin.info/aero/PLyHJZXNdCXsfqAkteaQ6JfZ_IHvxX-Hj3

[@shamilraj322]

Thank you for a very detailed explanation. :) Expecting more videos like this.

[@CodeDecode]

Sure Shamil. We will upload more videos on collection framework

[@TheFebruary10]

Very good to remember and recollect

[@CodeDecode]

Thanks Sanjeev 🙂👍

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Thanks a lot for the awesome content!!

[@CodeDecode]

👍

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Wow great mam thanks for this amazing video🔥

[@CodeDecode]

👍👍

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Very well explained! thank you

[@CodeDecode]

Thanks 👍👍

[@sekhar14301]

Thanks for wonderful explanation 🤝

[@CodeDecode]

You are welcome

[@ravikirantakale6616]

Thank you so much for such useful content 🔥🔥🙏

[@CodeDecode]

You are welcome.......

[@JourneyswithAK]

Seriously very great explanation ❤️

[@CodeDecode]

Thanks a lot 🙂🙂👍👍

[@alexandr7686]

You forgot top interface Iterable, please update collection hierarchy if possible or add comment. Thanks for video, waiting for next!

[@ammarzafar1337]

Very Well Explained.

[@CodeDecode]

Thanks Ammar 🙂👍

[@sasidhara2950]

Small correction-> Map interface does not "extend" the Collection not "implement". It really helped me to refresh quickly

[@venkatasaikrishnak6984]

Please continue and create video for internal working of hashset as well.

[@CodeDecode]

Sure👍👍

[@praveenagrawal9616]

Thanks for the video. It's really helpful for interview preparation. One small doubt I have in 6:57 you said hashset internally implements hashtable and one null value can contain. But hashtable doesn't contain any null key and null value.. Please explain and correct me.

[@arifpari9561]

You just nailed the Collections . One small request please do video on Collections on Java 8 prospective.

[@CodeDecode]

Sure will make a seperate video on Java 8 specific changes

[@neerajkbc]

Thanks for the video, really helpful 👍

[@CodeDecode]

You are welcome neeraj...

[@Rimanshu001]

Good one mam,please continue such videos.

[@CodeDecode]

sure we will upload more

[@ankush_in_sync5998]

Thank you. Keep it up.

[@CodeDecode]

You're welcome ankush

[@mohammedabraruddin9779]

yes i would love to see internal working of hashSet

[@CodeDecode]

kzbin.info/www/bejne/bZyTh4x-qrp5bMk

[@puneetsaneja3007]

I think you should also cover hashmap enhancement in java8. i.e from linkedlist to binary tree , when the linkedlist size increses. but anyways, Its nice and expecting more experience level questions on collection

[@CodeDecode]

Sure 👍👍

[@srikarwarrior123]

Thank you so much for the video :)

[@CodeDecode]

Thanks for writing back Srikar 👍👍

[@koteshwarvenigalla7150]

Great explanation!

[@CodeDecode]

Thanks..

[@maheshd3506]

Explanation was good,can do a video on soap web services

[@CodeDecode]

Thanks. Sure will make a video on rest web services soon then will cover soap too

[@sonalirajashri]

its very nice ad helpful.

[@CodeDecode]

Thanks Sonali 👍

[@rajatram5068]

Awesome Explanation

[@CodeDecode]

Thanks......

[@PallabChatterjee18]

That Map interface point it will be map interface does not extends the collection right ?

[@arunkumarmn7493]

Wow great explaination

[@CodeDecode]

Thanks 👍

[@vipinahuja6096]

Thanks for the awesome video. However, 18:40 you mentioned HashMap is slower as compared to its respective concurrent counterparts. But that's not true as HashMap is non-synchronized faster. Please correct me if I am wrong

[@avinashrawat5823]

very informative Thanks

[@CodeDecode]

Glad you found it helpful😊

[@Daxbedivlogs]

just subscribed your channel after this video.. thanks :)

[@CodeDecode]

M glad you find this helpful

[@sunitapawar1819]

Nice content.. Thanks

[@CodeDecode]

Welcome 👍

[@satishr2071]

Nice video keep it up 👍

[@CodeDecode]

Thanks ☺️