Internal Working and implementation of hashmap and hashset | Java Interview Questions | Code Decode

[@rahulagrawal3675]

Really liked the idea of explaining through slides also. And thanks for explaining the functionality for Java 7 and Java 8 separately; insightful indeed.

[@CodeDecode]

Thanks Rahul 🙂👍

[@praphulyadav4471]

I am really thankful for your videos I just wanted to share that Hashcode is not the parameter for branching in the collision. When a HashMap in Java (Java 8 and later) encounters a bucket with many collisions, it may convert the linked list of entries in that bucket into a balanced tree (specifically a red-black tree). However, the hash code itself is not directly used as the branching variable in the tree; instead, the key's natural ordering or a comparator (if provided) is used to maintain order.

[@sanyasee17]

The Best Video to understand Internal working of HashMap. Thanks a lot ❤

[@vijayavinayaktandur9599]

Thank you so much @code decode guys for your support. I cleared multiple interviews with your valuable videos. Hats off

[@CodeDecode]

thanks and all best Vijay for your future

[@shreyashachoudhary480]

Best video I've ever seen about HashMap's working!

[@CodeDecode]

Thanks Shreyash 🙂🙂

[@smitchaudhari9783]

This channel is underrated! Great work.

[@CodeDecode]

Thanks for nice words

[@ssbunny111]

Hi Mam, All you videos are excellent and very helpful to clear interviews. Your are doing this video at 1 AM... Hatsoff to your dedication

[@CodeDecode]

Thanks a lot 🙂🙂. Yeah that's when we get spare time after office ends 😃. We all are working IT professionals. Btw nice observation 👏👏

[@rajatgoyal2812]

I was searching for this type of video for a long time. This video is very informative and helped me better understand the concepts. Thanks for sharing such insightful content.

[@CodeDecode]

Thanks 🙏🙏👍

[@shekhar_sahu]

Thank you for taking us through the source code of these classes. I used to be afraid of checking such files. But this is how we get to learn good coding practice also.

[@CodeDecode]

Very true Shekhar. Very glad to see u are going through them. 👏👏👏

[@saivamsi4811]

Hi Mam! You are helping us a lot. Please keep teaching like this And also if possible please make a complete session on Collections frame work end to end. There are many tutorials on youtube, but nobody can teach us the way you do. I found your tutorials very helpful and easiest way to understand.

[@CodeDecode]

Sure Sai. Thanks a ton for the nice words. We do have videos on collection framwork. Can u plz tell what all topics u need apart from what are uploaded.

[@saivamsi4811]

@@CodeDecode Linked List, Stack, Vector, HashSet Vs LinkedHashSet Vs TreeSet..Thanks in Advance..

[@DevanshuKumar-o5r]

You delivered a nice explanation. It was needed for interview because it is important. I found this video and it helped me out. Thanks.

[@CodeDecode]

Thanks Devanshu 🙂👍

[@anison1111]

Simple and accurate explaination - good job

[@CodeDecode]

thanks

[@ArunSharma-hu4td]

Excellent explanation of internals of hashmap as well as hasheet with proper proof

[@CodeDecode]

Thanks Arun 🙂👍

[@ArunSharma-hu4td]

@@CodeDecodeone video for arrayList internals

[@kaushalchandra9824]

Thanks Mam for such à deep knowledge. God Bless you. Keep posting 🎉

[@aniketkalamkar227]

Wonderful video explaining exactly what changed with Java8. Can you please create one for ConcurrentHashMap as well

[@CodeDecode]

Thanks 🙂Sure Aniket 🙂👍

[@akankshasinha3352]

Thankyou so much dear❤ your videos are good to go for interview topics.. crisp and perfect .. Interviewer bhi khush hojaye😂

[@CodeDecode]

Haha Thanks a lot Akanksha🙂🙂 and we will be happy when u land at awesome job Girl ❤❤. Keep learning keep rocking girl 🎊🎊👍👍👍👍🎂

[@divyavegoti4609]

Have been checking all your videos..Inspiring work and content!!!

[@CodeDecode]

Thanks a ton Divya 🙂

[@raghuakuthota4900]

Too good of explanation :) thanks lot - great work - keep going

[@CodeDecode]

Thanks Raghu 👍🙂

[@sandiyr1989]

you r an amazing teacher..

[@CodeDecode]

Thanks 🙂

[@yasirakhn]

The content is really great, explaining everything in details which makes the internal working of HashMap and HashSet very clear. However, I have one question. Do we need this understanding for programming in real projects as generally we need to use HashMaps and HashSets to store and retrieve collection data and can also iterate using iterators, or is this just for interview purpose ?

[@GauravSharma-up9gs]

Thanks, Your channel is very helpful...

[@CodeDecode]

Thanks a ton Gaurav. It means a lot 👍🙂🙂👍

[@reshusinghal8298]

Ur videos are too good to prepare for interview. I have a question here. Whe linked list is converted into binary tree then which hash code is used to determine the left or right node? As per my understanding hash code of all keys is same because of which collision is happening so now which hash code to use for node calculation?

[@vickybhoir3017]

nice explaination

[@CodeDecode]

Thanks

[@ganeshahiwale4899]

Really liked the explanation can you please create a telegram channel so that we can have communication and polling advantage and discuss our doubts

[@vndprasadgrandhi7024]

Thank you very much.. Could you please do if possible tree set and tree map

[@CodeDecode]

Nice topic. Sure we will do that

[@rajyalakshmi3077]

Thanks! Could you please do a video of executor service future get and completablefuture from java how to handle if anyone executor service tasks takes too long

[@CodeDecode]

Nice topics Rajya, we will surely put video on these

[@vinayuddagiri]

Very good Explanation.

[@CodeDecode]

Thanks Vinay 🙂👍

[@krishnarohit3166]

Awesome Explanation

[@CodeDecode]

Thanks Krishna 🙂👍

[@sreejak6776]

Thankyou for the video mam

[@CodeDecode]

You're welcome sreeja

[@abhishekjain6559]

Nice explanation.. Great help .. thanks

[@CodeDecode]

Thanks Abhishek 🙂👍

[@anonymousxyz3856]

excellent explanation

[@CodeDecode]

Thanks 🙂🙂

[@akashkarn8429]

After finding such great videos, I am feeling blessed :D Thanks a lot !

[@akashkarn8429]

This is pure Quality Content !!

[@CodeDecode]

Thanks a lot Akash 🙂👍

[@phanimc11211]

neatly explained what changed with Java8

[@CodeDecode]

Thanks

[@aneelakar400]

Great explanation Mam.

[@CodeDecode]

Thanks 🙂👍

[@salmanpatel2968]

nice explanation keep it up we will support you and my request to you please make a video on time complexity and space complexity

[@CodeDecode]

Yeah that's s tough one to understand. We will create video on that soon 👍👍

[@salmanpatel2968]

@@CodeDecode thanks pl create on that topic

[@vaibhavjain8939]

Next Level

[@CodeDecode]

Thanks Vaibhav 🙂🙂👍👍

[@mahi2082]

Nice explanation

[@CodeDecode]

Thanks 👍

[@maartensnels3804]

Keep up the good work!

[@CodeDecode]

Thanks Maarten 🙂👍

[@amarthyaseshu683]

Thanks for sharing!

[@CodeDecode]

🙂👍

[@shivamanand9836]

13:32 “while converting the list to binary hashcode is used as branching variable” - couldn’t get this part as hashcode is same then they are getting converted to linked list and then equals method is being used to add the values in the linked list. So the question is if it has reached a certain threshold and then how different values of hashcode can come to get converted into tree?

[@simplegirl2218]

Mam, please make a video on multi threading concepts..with basic and advanced ..

[@CodeDecode]

kzbin.info/aero/PLyHJZXNdCXsdUXzeeBZIADof_U-40jBJO

[@jeebamvarghese3542]

Great explanation

[@CodeDecode]

Thanks Jeeba

[@krishnan6201]

can you plz explain about memory allocation enhancement in 1.8 feature.

[@shashwatidash8524]

I have a doubt if anyone could help. Since all entries within a bucket index have the same hash code (due to being placed in the same bucket), how can the hash code determine an Entry object's placement to left or right. Instead, the Comparable interface or custom comparator only will be used to maintain the ordering within the binary tree. Am I getting it right? Since not the whole bucket is changed to a Binary tree, only a particular bucket index is!

[@chinmayd4093]

@shashwatidash8524 as per my understanding, the first element(for particular bucket) which you will be adding , will be acting as root node of that tree.

[@sravanreddyreddy3562]

Just a feedback - There is too much of juggling btw screens...

[@CodeDecode]

Understood. We will try to reduce it. 👍👍

[@jerinxavier5380]

How can we use hashcode to compare elements while adding to the binary tree. Unless the hashcode was the same we wouldn't push in the same bucket. Right.?

[@vengateshm2122]

Thank you!

[@CodeDecode]

🙂👍

[@aswinkumar6796]

Hi I have one doubt In bucket, all elements with same hascode only? Is it possible, different hashcodes in same bucket as you mentioned in video@13:59?

[@anisha9709]

I guess it should be when 2 keys that are different but having same hashcode?

[@kudumulasivaramakrishnared6379]

Please continue all data structures (linear,non linear in graphs, hash table)

[@CodeDecode]

Sure 🙂👍

[@kamallochannayak2706]

Great mam...

[@CodeDecode]

Thanks 👍🙂

[@rahulingole4923]

still usefull video

[@CodeDecode]

😊

[@kanchankatkar5226]

If same hashcode is there then what will happen in binary tree fornat how key can be comparable will you give example, it's confusing for me

[@rajatgoyal2812]

At 14:12 you mentioned that in tree the main comparison will be on the basis of hashcode, But in a bucket when there are several entries and all of them have same hashCode then how are we comparing on the basis of hashCode.

[@rasolutions8676]

Dose Linked List in the bucket (specific index calculated after hashing) is going to convert to tree or is it the complete bucket is getting converted into tree a) if it is linked list at specific bucket index then how the hashcode less or greater then calculation will happen as per me at that point hashcode would be same for both element isn't it? b) if the complete bucket is getting converted into tree then why we are saying linked list will get convert to tree...if i heard right! 🤔🤔🤔 Please help me understand the concept

[@arinbose6366]

Thanks but do you have video of say passing hashmap as parameter etc

[@CodeDecode]

What do u need? M unable to understand the requirement. Can you plz elaborate?

[@arinbose6366]

@@CodeDecode I was looking for below found it ,in future can you show some examples like say taking hashmap as parameter, taking hashmap returning list etc, no need for video you can post in github that would help, for you these might seem very simple and common task but for starters this would help a lot,thanks again for all your videos. // returning hashmap public HashMap asHashMap( K[] keys,V[] values ) { HashMap result = new HashMap(); if (keys == null || values == null || keys.length != values.length ) throw new IllegalArgumentException(); for (int i =0; i

[@arinbose6366]

@@CodeDecode I had just given a suggestion,otherwise learnt a lot from your video series 👍

[@tejasnerkar1330]

do you have link for all the presentation slides that we can access? It will be really helpful to go through it as a revision before interview.

[@satyajeethukkire6099]

Maam, most of the comment section has the doubt of collision at 14:29 please explain the doubt, it is really confusing

[@suvch5842]

Do you have any java course from beginner level to advanced in Core to Advanced java

[@shivachanda2438]

Very good explanation, but I have a doubt: while explaining handling collisions in java8 nd above, u mentioned that if the hash code is same in a bucket, then we go with comparing keys , but collision is caused because of same code na, my doubt is all the entries in a bucket will having same hashcode ryt that is how they are placed in a bucket , keys may be different but hascode remains same based on hashcode only we are choosing the bucket na, please clear my doubt.

[@CodeWithCB]

All entries in a bucket may not have same hash value though they will have same index. Remember we first calculated hashcode which again converted to some hash value. This hash value is then mapped to some index. And this is the point where two different hash values may result in same index. So while doing get operation first hash values are equated and then keys are equated.

[@shivachanda2438]

@@CodeWithCB sry what do u mean by hash code and hash value both are same ryt , for a given key we will find hashcode , what is hash value. I didn't get u, please elaborate

[@CodeWithCB]

@@shivachanda2438 internal implementation of Hashmap frist calculates hashcode of key as per hashcode() given for key object. Then internally it converts this hashcode to hashvalue h using formula (h = key.hashCode()) ^ (h >>> 16) . This is done to spread keys across the array causing less collisions. And this hashvalue is used further to find actual index using formula index = (n - 1) & hash.

[@noorahameds8]

How will it work if the value is a list Map m = new hashmap();

[@RANDOMGAMER-nq6jf]

14:29 im having doubt on why there will be different hashcodes in same bucket??

[@chiragshah9171]

Yea.. same doubt. Linked list gets created when there is hash collision then how can be there different hash code values

[@chiragshah9171]

14:29 how can we have different hash values if there is hash collision, it's bit confusing there 😮

[@djinthemix33]

I hope to be that fortunate winner... Plz Like✓ SHARE✓ SUBSCRIBE✓

[@hackstreet781]

From where do you learn Java ? I also want to read from there.

[@CodeDecode]

Mostly docs helps us a lot in understanding the concepts

[@arulantony2137]

traversing linked list and tree logn and O(n) then how hashmap complexity isO(1) ?

[@CodeDecode]

It's said best case complexity o(1) worst case o(logn)

[@Sanjaykumar-nz4tf]

Hi Mam, I have a doubt in the put() method of hashmap.. If the hashCode of few keys are same means all those will be stored inside same bucket in linked list format (if threshold is increased by 8 means it converts to balanced tree) * Right branch will be higher value of hashCode and left will be lower than that.. My Doubt is all the variables present in same bucket will have same hashCode.. Then how they will be compared while storing in balanced tree?

[@AshishKumar-vj7fq]

I also have the same doubt. How different hashcode can be present in same bucket because different objects will land on same bucket only when hashcode for them is same.

[@malaiarasi4400]

Hashmap concept was awesome.. Hashset is not much clear.

[@CodeDecode]

How can we help Malai? What is unclear can u plz tell us so that we can clarify that to u?

[@malaiarasi4400]

Mam i went through the video again now it's clear. Thanks

[@CodeDecode]

Awesome Malai 🙂👍

[@9-1939]

👌👌👏👏👏🙏

[@rohitkapade1130]

14:29 in second point how come is this possible that in one bucket will have keys with different hashcode as we assigned bucket on basis of hashcode itself. I guess binary search tree is based upon keys.

[@RANDOMGAMER-nq6jf]

I'm also having the same doubt. The hashcode enters the bucket only if it is same and the keys are used to compare amongst the elements in that bucket. Im confused here..please explain here....

[@lakshmaiahyannagiri291]

please share the document of this class

[@CodeDecode]

Which document are you asking for Lakshmaiah?

[@kanikanarwat826]

Hi what will happen if we have overriden equals method but it always returns true.

[@MHK958]

Just do it in eclipse, if equal returns true every time then i think hashmap will store only 1 key if same has code come

[@PankajPatil-kw9ic]

1:27 Explain slowly

[@prasadsatpute5197]

Didi please please please please Me and You not going anywhere. If we learn well or quickly, it does not mean that you speak so fast. Please explain with some breath at normal speed or read calmly bs itna kahen hai please mam please

[@harshwardhanshetty4683]

use chatgt thats way more clear

[@BaluKompalli]

Explanation fine but i am unable to catch that flow. Listened more than 3times. Little bit confusion. Could you please explain in less technical way. Atleast one simple example

[@CodeDecode]

Sure we will do that👍👍

[@BaluKompalli]

@@CodeDecode I listened in very slow motion and put a diagram in a paper. Then i understood the concept. I think it is fine for me. No need to do any other video with examples. Another thing is , I tried to donate thank you, but not redirecting to payment page. Will check and update you again.

[@koushikpan1320]

why is your voice shivering. Looks like you are worried of something. 👀

[@CodeDecode]

It might be cold here or mic u Issues. Not sure. We will check 🙂👍

[@akshayaggarwal6364]

it was bit confusing

[@suhilirshad]

very confusing explaination . please make it short and understandable for interview pont of view purpose

[@saaii9]

Hi mam can I know your name

[@CodeDecode]

Hello. You can call us team code Decode ❤️. Happy to be connected 🙂

[@amitmapari393]

Bad explanation

[@CodeDecode]

Hi Amit. Can you please suggest what went Wrong ? We will try to rectify the issue you faced

[@siva-m2t7o]

Vest fello

[@MHK958]

Awesome explanation

[@CodeDecode]

thanks

[@vickybhoir3017]

nice explaination

[@CodeDecode]

😊