Java Interview Questions and Answers for Fresher and Experienced [MOST ASKED ] Code Decode

In this video of code decode, you will learn Java Interview Questions and Answers for both fresher and Experienced in Java which is important in Java Interview Questions and Answers in Telephonic Interview
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What is the difference between ArrayList and LinkedList ? 00:22
01:26 What is Lazy Initialization in Hibernate ?
02:50 Difference between first level and second level cache in hibernate
04:00 Difference between HashMap and Hashtable?
05:32 Describe, in general, how java's garbage collector works ?
08:15 What is Serialization ? Why do we need it ?
09:09 What is Dependency Injection or IOC ( Inversion of Control ) ?
10:17 What is Weakhashmap ?
12:20 What are functional interfaces ?
13:44 If synchronized map is there why concurrent hash map was introduced
Most Asked Core Java Interview Questions and Answers : • Core Java frequently a...
Advance Java Interview Questions and Answers : • Advance Java Interview...
Java 8 Interview Questions and Answers : • Java 8 Interview Quest...
Hibernate Interview Questions and Answers : • Hibernate Interview Qu...
Spring Boot Interview Questions and Answers : • Advance Java Interview...
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GIT : • GIT
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[@CodeDecode]

Hey Guys, These are the Questions which we face mostly in the first round of Giant MNC's like Infosys, Accenture,Amdocs , Deloitte, IBM etc If you have faced any other questions please comment down below we will cover that in next part.

[@akashkeshari8927]

For what experience range, these questions are asked?? Fresher level??

[@CodeDecode]

0-6 years. First round / telephonic / skype / Teams

[@srijith431]

I have experienced few more questions like 1) what is CI/CD ? 2) internal working of hashmap 3) what is bean creation exception ? 4) and some questions like how to commit in git. 5) and about junit

[@srijith431]

@@CodeDecode but I don’t think wipro , IBM , Accenture , Infosys are conduction telephonic rounds.

[@CodeDecode]

By telephonic we meant teams, skype, google meet, etc. And in covid situations, yes they are. Are you able to go to office to give interview? Because our team couldn't

[@javier.alvarez764]

1. LinkedList vs ArrayList? - arraylist better for storing, linkedlist better for manipulating data (insert, update, delete). 2. Lazy initialization - only fetch data when needed. 3. Difference between first level and second level cache in hibernate *1st level - by default enabled - associated by Session - when session gets close your cache gets lost - only accessible by the session that maintains it. *2nd level needs to programmatically enabled - associated by SessionFactory - accessible to whole program 4. HashMap vs HashTable HashTable - synchronized - thread safe - does not allow null key or null value. HashMap - not synchronized - not thread safe - only allows 1 null key - can be synchronized using Collections.synchronizedMap(hashMap); 5. What is Java Garbage Collection? - 6. What is Serialization? - converts object into byte stream to transmit data. 7. What is Dependency Injection or Inversion of Control? - instantiation is handled by the framework. 8. What is WeakHashMap? - 9. What are functional interface? - only has one abstract method, but can have multiple default and static method. - use as reference to lambda expression. 10. Why is there concurrent hash map if synchronized map already exist? - performance issue in synchronized map. - SynchronizedMap acquires lock on the entire Map instance , while ConcurrentHashMap divides the Map instance into multiple segments and locking is done on those. - ConcurrentHashMap is therefore faster because of these.

[@CodeDecode]

👍👍

[@nvjrane]

This seems like a short 15 min video, but the study behind it must be so deep to have your concepts clear and present it concisely to us. I have never learned so much in the last few months that I learned in this short video. Keep it up!

[@CodeDecode]

Yes that's very true Nitish. Thanks for recognizing our efforts and putting that up in such a nice words 🙂👍👍. Thanks a lot 👍👍

[@ashisdalai5369]

Lucky we get it in 15 min

[@virendra872]

​@@ashisdalai5369 AA

[@usamaansari7903]

i always prepare more with defination but while giving interview I could not able to ans what I had learned word to word just like u..u r giving word to word ans...this much of confidence and concentration I want as a fresher

[@CodeDecode]

Thanks Usama 🙃👍👍👍

[@addminblaze]

I dont think anyone wants you to give word to word answer, rather knowing concept and working principles will help. You can use analogies to explain concept, PS: dont over do it. You can explain it in your words and thats all needed to crack the interview.

[@handleOfASK]

It’s like you know all my doubts and you are clearing one by one😂. Awesome… Thank you 😀

[@CodeDecode]

Thanks 🙂🙂

[@handleOfASK]

😄😁. One request please make a video on.. Java Memory Management in depth.

[@CodeDecode]

kzbin.info/www/bejne/e5a1d4KMgstqqKc

[@CodeDecode]

There are 2 parts, it covers memory management in java

[@CodeDecode]

kzbin.info/www/bejne/mKaUY315icqKhdE

[@pranjalrathod8556]

Can we have multiple mock up interviews like this please? Your contents are really one of the best out there 🙏

[@CodeDecode]

Sure. We will continue this series. Don't worry 😊

[@mrunalinimistry6621]

just hats off to you @Code Decode team. Really helpful. Love from gujarat

[@Truth_12349]

These kind of videos are very helpful to brush up concepts before interviews.

[@CodeDecode]

Thanks Vishnu

[@SanatanBelievers]

13:57 That's very nice question was epic🤣

[@CodeDecode]

😜😜

[@veena618]

Request you to please keep written explaination in description as you were doing in earlier videos it will help us to have quick round of glance.

[@CodeDecode]

Sure Veena. But we usually go out of space in description, hence couldn't cover all.

[@veena618]

@@CodeDecode okay no issues👍

[@akaashkumar4926]

Hi Mam, Great work! Can you please make separate playlist on Spring Boot Microservices? Now a days Spring Boot means they are expecting microservices as well to be known! Please do consider this request

[@CodeDecode]

So true Akaash. Will surely do that👍

[@srashmitha8953]

Found very helpful ,Please Write Explanation in description ,like your previous videos..!

[@CodeDecode]

Sure 👍👍

[@AshishSharma-mf4sg]

you are going good🤩 Just need to add some basic questions which was tricky and even basics .. that would help in interview

[@vinodkarathiyaofficial]

It was amazing. Request you to make detail video on Garbage Collection.

[@coderdostayush2032]

Mam your explaination is just like 3 idiot movie ❤️. Thank you so much for making our journey so easy. God bless you❤️

[@CodeDecode]

Thanks for the motivation Ayush 👍

[@kazaasekhar]

happy to watch it again and again

[@CodeDecode]

Thanks sekhar

[@shobhitagarwal8151]

Hey, I really liked all the questions you choose. All of them are very good questions. Explanation of garbage collector working is too knowledgeable. Hoping another great video for round 2. More power to you guys.👍

[@CodeDecode]

Thanks Shobhit 👍we will create soon 👍

[@dynamicdeveloper6658]

All videos are amazing Great informative

[@CodeDecode]

Thanks a lot 🙂👍

[@vamseedhar2482]

Good stuff and excellent explanation

[@CodeDecode]

Thanks Vamsee 👍👍

[@vasundharasannidhi5210]

This is very helpful. Thank you. Please do for experience level interview also.

[@CodeDecode]

Sure Vasundhara. We will cover them too soon.

[@jithendrareddym9149]

Hey

[@anuhyabolla7891]

can you make interview questions on core computer subjects?

[@GaneshSingh1]

Do you have any pdf Or ppt stored in gdrive? If you have please share the link So that we can directly download the answers, it will so fast for the revision.

[@anilmaurya55]

Very helpful, please keep the good work thanks

[@CodeDecode]

you're welcome anil

[@scrppr8270]

Great..nicely explained... Can you please make similar video on Multihreading concepts...specially Concurrent API

[@CodeDecode]

Sure. We have 2 videos on multi threading. Will create more on concurrency

[@scrppr8270]

Yes saw those 2 videos...they are also too good😎...but some concepts are to be covered....please cover those as well🙏

[@CodeDecode]

Sure. We will cover them soon 👍👍

[@akshayengineer2018]

You are Amazing... Thank you so much mam 😊

[@CodeDecode]

Thanks Akshay 🙂👍

[@mohamedely3987]

You are doing a great job 👏

[@CodeDecode]

Thanks

[@vry2652]

great videos , it could be more helpful if you show snippets code while giving response

[@CodeDecode]

Sure👍🙂

[@muralikommuru5992]

Its really great and really covers a lot of concepts, I mean it’s kind of go to if you have less time for preparation, your videos. I would surely look forward for more videos and also will like to suggest you if you can make videos on advanced stream operations for example group by with having, partitioning by, etc as they have overloaded methods with different numbers of parameters and really there is less content related to this outside, which explains each method variant need with examples. It will be nice to watch those videos if you can try them as well.

[@CodeDecode]

That's a very nice suggestion Murali. Will surely do that 👍🙏

[@GAGamingLegends]

Love your videos, please upload more ❤️❤️❤️❤️❤️❤️❤️

[@CodeDecode]

Sure 👍👍

[@boobalakrishnan6610]

Answers are very clear and unterstable good job :)

[@CodeDecode]

Thanks Boobala 👍🙏

[@sureshgarine]

nice explanation madam. thank you

[@CodeDecode]

Thanks Suresh 👍

[@karthikeyanrm3446]

It would be good if you can make more videos on Spring core concepts & interview questions - DI, IOC, Autowiring etc. Also any other important concepts in Spring

[@CodeDecode]

Sure Karthikeyan we will make it soon....

[@kaushikigoel759]

This video is gold!!!

[@CodeDecode]

Thanks for the nice words kaushiki

[@Manu-et6zk]

Answer to dependency injection question was like : "dependency injection only happens/used in spring applications", and its main advantage was not at all mentioned.

[@CodeDecode]

Dependency injection happens in angular too. It's constructor injection in angular.

[@CodeDecode]

We will cover all of them Manu, in 15 minutes we tried our best to deliver the most. We know that your time is precious. 🙏but we can't cover every thing in 15 minutes. Thanks for your patience and for your suggestions 👍👍🙏🙏🙏🙏

[@ashishpal5446]

Always giving out best content ✨ Thank you very much for this!!

[@CodeDecode]

Thanks Ashish 🙂👍

[@abiultimate]

Awesomeness 👌 👏

[@CodeDecode]

Thanks Abirami 🙂👍

[@arijitmohapatra147]

Mam can u help me where to learn adv java plsss 🙏

[@anjalijaiswal1750]

One question mam - How Garbage collector knows it is a unused object?

[@CodeDecode]

If no references are found that means object is unused. Object o1 = new Object ; O1 is a reference. If I do o1 = null then no reference exists.

[@start1learn-n171]

TQ

[@codenexa1666]

At fresher level they will ask this type of questions like spring, hibernate ?

[@CodeDecode]

Yeah these are very basic questions of spring hibernate. They might ask you. Because java is just a language, spring hibernate are frameworks. You might use them in your college major projects 👍👍

[@SaahilShaikh]

great video 🙌

[@CodeDecode]

Thanks Saahil

[@vrushalifasate2052]

Employee object is stored in arraylist .How to sort entities store in object like name ,I'd .

[@CodeDecode]

Collections. Sort(l, customComparatorObj)

[@vemulasoumyasri830]

Nyc explanation mam thank u soo much mam waiting for more videos mam🙏🙏

[@CodeDecode]

Sure Vemula 👍👍

[@jithendrareddym9149]

Hello vemula

[@jithendrareddym9149]

@@vemulasoumyasri830 you are working ah?

[@jithendrareddym9149]

@@vemulasoumyasri830 mari?? Inkenti?

[@vemulasoumyasri830]

@@jithendrareddym9149 y???

[@nikhilsharma-kd4pi]

For which profile these questions are for??

[@CodeDecode]

Java full stack developer. Currently this first video has only JAVA questions.

[@gokulaher2476]

ConcurrentHashMap in java internally uses a new more sophisticated technic calles as segment , number of active threads doing write/update operations is == number of Segments, each bucket in HashMap is belong to one segment and In ConcurrentHashMap Lock is striped and only that segment is getting lock on which write/update operation is performed So multiple write operations can performed by multiple threads on multiple segments concurrently Because now Lock is on segment level and not on entire HashMap

[@CodeDecode]

Thanks for explaining it again Gokul 👍👍🙂🙂

[@uvanana.]

Your videos all good, try to talk a bit slowly .,otherwise your videos are awesome

[@CodeDecode]

Sure ❤️❤️👍👍 we will reduce the pace👍

[@shrutikorke2368]

Make interview questions on rest api

[@CodeDecode]

Sure Shruti. Next we will create on them too. We will include restful web services too

[@soumyakantpani9923]

Hey Guys,Could you just make a vedio of annotations in spring and rest?

[@CodeDecode]

Hi saumyakant we have created 2 videos on annotations please check that out

[@Ravikumar-nf2mu]

can u make a video about microservices interview questions

[@CodeDecode]

we will make it soon

[@start1learn-n171]

Tq

[@soumyakantpani2997]

can you just make vedio about spring batch?

[@CodeDecode]

Sure Soumyakant 🙂👍

[@usamaansari7903]

this is for freshers ??

[@CodeDecode]

For any one trying for java profile

[@Ravikumar-nf2mu]

what is the difference between named query and native query

[@madhu56236]

Can I know your experience

[@CodeDecode]

We are a team of IT people having experience varies from 2-8 yrs

[@madhu56236]

Oh that's great thanks to you and your team🙏

[@CodeDecode]

👍👍🙏🙏

[@jithendrareddym9149]

@@madhu56236 entha experience??

[@muraliram2582]

you are laughing when you are giving the garbage collection answer

[@amitdubey2793]

Too many ads, makes this beautiful video annoying.

[@CodeDecode]

Not in our hands much Amit. It's KZbin who fits ads in between.

[@amitdubey2793]

@@CodeDecode can understand. Kudos for your work 🎊. I have my interview today on java and referring only your channel.

[@CodeDecode]

All the very best Amit. We wish You rock in your interviews Man. Keep learning keep Shining 👏👏👏👏🤞🤞

[@srijith431]

Good one 👏🏻 also please post some scenario based Q & A which most often asked in interviews 🙏🏻 also please let me know your instagram id

[@CodeDecode]

Thanks Sri ....... Instagram : instagram.com/codedecode25/

[@srijith431]

@@CodeDecode thank you so much incase of any doubts in subjects it okie to contact thru instagram ?

[@CodeDecode]

Sure Sri. You can any time reach us. We are always here for you👍

[@srijith431]

@@CodeDecode thank you team 🙏🏻

[@CodeDecode]

🙏🙏👍👍