For anyone confused about how the index value is calculated: the “&” operator is a “bitwise AND” operator. When it is used, both its operands (the numbers before and after the operator) are converted to binary, and a bitwise “and” is performed on each pair of matching place values in both binary numbers. This results in a new binary number. For example: 12 & 5 = 4, since 1100 & 0101 = 0100 And also 2306996 & 15 = 4, since 1000110011001110110100 & 0000000000000000001111 = 0000000000000000000100

@coding_ss632

4 жыл бұрын

Thanks Rick

@MuzicalMelody

4 жыл бұрын

How to get the hash value

@yaruiwu7408

4 жыл бұрын

This is just wonderful

@balajikoc1429

4 жыл бұрын

Thanks Rick

@adarsh6750

4 жыл бұрын

Thanks rick

I think I will add one more point at 7:50, When you call put() for the element having the same index or hashcode() it calls equals() method as well to compare the key. If it's same then it will overwrite the previous element and if not then append to the next node. This part is very important because once I was asked what will happen if you only implement hashcode() and not equals() or vice versa.

@mohsensm7438

3 жыл бұрын

This point is very necessary to complete this good video.

@PavanKumar-yj8fu

2 жыл бұрын

Very good point, thanks

@ArkAngelHFB

2 жыл бұрын

Would this mean that without the equals() method call, a HashMap could erroneously overwrite both Key and Value at the same time?

@dmitrikonnov922

2 жыл бұрын

@@ArkAngelHFB no, it doesn't make sense to overwrite the key, because its already in the array. Instead, the value is overwritten, because the hashmap doesn't tolerate duplicates. This can be also tricky when we deal with children nodes, for instance with one-to-many relationship. Sometimes one's better of to override children's hashcode() based on their class only, so that all children (objects of the same class) have the same hash code.

@ArkAngelHFB

2 жыл бұрын

@@dmitrikonnov922 But without the equals() call, wouldn't it just assume that since it shared the same hash, it WAS the same key and overwrite it?

HashMap working animation + enhancements for HashMap in Java8 - check out! If you liked, please leave a comment!

@chilltouchng

9 жыл бұрын

+Ranjith ramachandran Really good! This is the best tutorial about "How HashMap works"!

@ChandrakanthReddySoodiReddy

8 жыл бұрын

Very Helpful video on HashMaps. I actually understood how Look up works. Thank you...

@atulkumar-hm6yo

8 жыл бұрын

Sir,Please share how Hashcode made...!!!!

@satyaprakashnayak1363

7 жыл бұрын

Very wonderful tutorial....Can you please also explain in animation How ConcurrentHashMap and ConcurrentLinkedQueue works?

@kinjalthehero

7 жыл бұрын

Thank you

This is the best tutorial I found for "How HashMap works"! Demo using animation is remarkable :)

I'd like to add a point to the wonderful explanation of HashMap implementation When HashMap reaches its threshold limit of .75 or 75% it re-size by creating a new array of double the previous size HashMap, and then start putting every old element into that new bucket array and this is called rehashing and it also applies hash function to find new bucket location.

@satishpatil115

6 жыл бұрын

for any object the index will be 0 to (n-1) when we take mod of (n-1), then why we need to re-index or it re-sizes ???

@ayushjindal4981

6 жыл бұрын

we need to do it so that get and put operations can be done in O(1). if we dont do it, the size of linked lists would keep on increasing and would eventually increase the cost of operations.

@vishalkumargupta7986

5 жыл бұрын

It does not take double size but size equal to next power of 2.

@v0nnyboy

5 жыл бұрын

You're implicitly stating that it's double ... as a previous power of 2 ( 2^4) is being multiplied by 2 .

@ayushman_sr

5 жыл бұрын

this was important part... yet nit covered

This is probably the best explanation of Hashmap I've come across! Kudos to you!

This HAS to be one of the finest tutorials I have ever seen. The use of the animation was extremely well thought out and makes the subject so clear even a non-developer should understand it! Very well done! Thanks for your efforts Ranjith.

People who has disliked, what are you guys expecting ? This is just perfect explanation!!

@javatmz

5 жыл бұрын

:) right

Right on my dude. I've been struggling with one specific piece of the implementation (what we do with the hash code), but this video explains it perfectly. Thank you!!

Holy shit I was confused about hash tables for so long and this video simplified in such a nice way.

Best explanation. Perfect

my friend, I wish i saw this 3 days ago.... I didnt learn anything new because I have been studying hashMaps pretty aggressively the last 3 days, but my life would have been A BILLION TIMES BETTER if i found your video first. Beautifully detailed and easy to understand! TO BEGINNERS, THIS IS THE BEST INTRO TO HASHMAP VIDEO ON KZread!

Great explanation. The only point I feel missed was when two keys have the same hashcode the Node actually overrides the original nodes and doesn't get appended to the Linked list. Your run case could have included this scenario.

@jasper5016

2 жыл бұрын

Good one brother

@vyshnavramesh9305

9 ай бұрын

both hashcode() and equals()

I was looking for a good explanation for a long time, and I found today. Thanks, Ranjith.

This is the best explanation available in youtube for Hashmap...!!

Great explanation. If anybody want to know how HashMap internally works please watch this video once. Thanks for sharing such amazing video.

This is the best video that I have seen by now, however its sad that you have stopped posting now

This is an in-depth very well explained video! Thanks a lot!

@ranjithramachandran5928

8 жыл бұрын

Thanks!

@arvind143100

4 жыл бұрын

@@ranjithramachandran5928 Hi, Sir, I have a doubt, kindly explain plz. My "Eclipse IDE" showing two hash value for key "apple" (and for others key too), i.e, 93029210(index = 10) and 93030097(index = 1). According to formula it should be index=10, but it is placed at index= 1. Kindly, explain why we get two hash value for each key, and why its index is 1 and not 10. 🙏🙏🙏

@komirellykasanaboina5597

3 жыл бұрын

@@ranjithramachandran5928Hi sir Nice Explanation and I have a small doubt, could you please explain once,In MAP, If two Entries having same key and same hashcode?? HashMap map=new HashMap(); map.put("101","hdfc"); System.out.println(map.put("101","sbi")); //Returning value is = hdfc //After iterating Map, and getValue() method returning = sbi Could you please explain why it's print 'sbi'', How about hashcode and equals method work in this case????

Ranjith, You have Awesome teaching skill. Without any doubt , This is the best explanation of Hashmap . I experienced the same ease of my understanding regarding your garbage collection in Java explanation too. Cool.

Excellent explanation with example of how hashmap put and get method works internally.

Correction: Whenever there is collision, the new entry should added as the head of linked list, not tail.

@sameer_sah

3 жыл бұрын

any references ?

@sergeyvechkitov221

3 жыл бұрын

p.next = newNode(hash, key, value, null);

@bsaikumarreddy1413

2 жыл бұрын

Yes. Because the insertion will take O(1) time by inserting at head rather than tail.

this is awesome explanation dude.. The best one for HashMap

@ginny5967

3 жыл бұрын

😭

@ginny5967

3 жыл бұрын

R

@RagPeddabudi

3 жыл бұрын

@@ginny5967 watzup buddy ?

@RagPeddabudi

3 жыл бұрын

@@ginny5967 wat made u cry

This got to be the best explanation of Internal working of hasmap that I have ever seen. Thanks..!

Excellent demonstration of HashMap implementation!!

I learned a lot about Hashmap from this video. Thanks a lot Ranjith, you have did a great job. :)

Excellent job @Ranjith ramachandran! Keep doing it!

HashMaps finally demystified. Thank you very much

It's really sad that you aren't posting videos anymore. you have such great talent in teaching and you were a valuable resource on youtube.

Hey Ranjith Very detailed and nicely animated work..It was easy to understand

Dude more videos please :) You are awesome :)

Your videos are very thoughtful and to the point You should start making more of such content - Watching this in 2014

Splendid explanation with Animation. I have been using HashMap more than decade. Now, I got clarity how it works internally. Thanks for the commendable work!!!👏

Good explanation, but can you remove the recording of yourself, frankly it is a little disturbing to watch your head tilt frequently.

@rhimanshu6288

7 жыл бұрын

true

@nirmitsrivastava

7 жыл бұрын

true

@rexroy4037

7 жыл бұрын

yes its kind of disturbing ..

@shubhamsrivastava5400

7 жыл бұрын

lol

@ahmetemreboyaci

7 жыл бұрын

well that's ungrateful

Hi Ranjith, In the first put operation scores.put("KING",100). your index comes to 4. But according to index = hash % (n-1) it should be index = 2306996 % (16-1) this gives 11 and you calculated it as 4. However, if we put 'n' instead of 'n-1' we will get result as 4. So either the formula hash % (n-1) needs to be changed to hash % (n), if you are calculating indexes correctly or if the formula is already correct, your index must come out to be 11. need your comment on this. thanks

@ranjithramachandran5928

8 жыл бұрын

+Vincent Lal Please note the index is calculated as hash & (n-1) which is same as hash % n-1

@raju5081

7 жыл бұрын

it should be n only as the operation always outputs 0 to 15 which are indexes of the table 0 to 15.

@_Vaibs_

7 жыл бұрын

+Vincent Lal Wondering how you can calculate like that. Do it bitwise . 2306996=1000110011001110110100 , (n-1)=(16-1)=15= 1111 , 1000110011001110110100 AND 1111 = 0100 which in decimal is 4.

Really good explanation with the help of animation.

uploaded 9 years ago, still an golden explanation till date.

During put operation, why did we need to compare the hashcode, only comparing the keys will work. Say for an instance two keys have a same hashcode, in that case comparing with hashcode takes you no where, you have to compare key. May be I am missing something, please correct me I am going somewhere wrong.

@etofok

7 жыл бұрын

keys are objects, you'll need to run .equals(). integers are much faster to compare via "&"

@skullwise

6 жыл бұрын

I had asked the same question. :-)

How hash(k) is calculated? Can you please explain..

@ranjithramachandran5928

8 жыл бұрын

+Yogesh Bhat - hash(k) in real implementation is done to address "poorly" implemented hashcode methods in classes, that will cause a bucket(or index) loaded with too many nodes(or in older terms entries). It basically spreads higher bits of actual hashcode to lower order. This is done because the modulo operation produces different results only based on lower order btis.(in base 10, think of numbers at 'ones' position)

Great and useful information with clear explanation and awesome animation. Thank you.

hands down this is the best video on how hashmap works internally. Thank you very much.

Your face is in the way of the slides. lol

dude stop coming back and forth in to the screen. Its distracting

Best video i have ever found in you tube regarding implementation of hash map .Described it clearly

Best explanation from all videos I looked on yt.

perfect video to learn how hashmap works in a very short time.

Wow, this is the best tutorial about itHashMap on KZread!

So helpful and explained in a very simple way

This is just crystal clear explanation!! The best explanation for hashMap!!! And thank you for the information about the updated hashMap in Java 8. That's so cooool and smart!!

this is THE BEST EXPLANATION of HashMap...thanks

very lucid way to present the explanation, awesome, thanks alot.

Exceptional presentation of HashMap. Keep up the good work :)

This is the first explanation that has made sense to me! Its like an epiphany! Thank you!

Very Nice explanations Sir thanks a lot... for sharing

Nicely explained! Thanks, keep creating !!

One of the best resource on HashMap. Really stunning !!!

Absolutely fantastic use of animation for presentation. understood in one shot. Thanks for taking the pain of wonderful preparation. excellent work!

The best! ...and I knew nothing about this complex topic before the video, but now it's my favorite, thank you!

Use of animation really helps understand the concept. Thank you so much sir 🙏

Great explanation about hashing and collisions...

I like when I can see the lecturer on the screen. Good explanation, this is what important in here

Very Good Explanation for Hashmap implementation..Thank you...

Quite awesome..... presentation with nice crystal-clear language.....so nice....so much helpful.....I was so confused from last 4-5 years.....but today its remove all deadlocks of confusions and misunderstanding about hashmap's Internals......

Recommended video Simply explain how it happens well done

Very good video! Thank you for your explanation.

Nice presentation with animation. Thank you...

Thanks Ranjith for tutorial. After referring to tutorial I visited the actual source code of Hashmap and now its pretty much clear about the functioning of put and get method and also about resizing of the table size when it reaches the threshold.

Earlier i though it would be very complicated concept but sir you made it so simple. thanks

awesome explain about HashMap

Best tutorial for understanding HashMap. Thanks a lot !

Amazing explaination and animation!! Love it.

Very well explanation of HashMap .

Good tutorial for hash map implementaion

This is the tutorial on hashmap I have been searching for...great job...very well explained...thank you

Thanks for sharing knowledge It helped me to understand.

Awesome Explanation , now i got the clear idea of how HashMap internally works, thanks a lot.

Too good!!! thanks for helping me to understand the internal hashmap work in java

Awesome explanation .thanks a ton.

Very nice explanation. Thank you Sir.

I really like visual explanation, Appreciate you and thanks to share

simple explaination. Nice video

Superb video explaining HashMap. Best i have gone through for any topic on Java. Please post more videos, would love to hear on many more Java topics from you.

very well explained .. Thanks for sharing!

Excellent explanation with animation. great going and thanks.

liked, subscribed and i can never forget hashmap implementation for life time now.

Now i have got the detailed knowledge of hashmap.... Thanks

Superb explanation Sir, keep it up and keep aspirants enhance their skills.

Its always a good time while watching your precious and informative videos. Very good and easy to understand. Thanks alot

Excellent Video on HashMap

The best explanation for hashmap internal working. Thanks man.

this is the best explanation on the internet

Very Good explanation and Animation...Thanks

Great explanation ever seen

Classic video on HashMap... Please keep on posting such classics

Ranjith with the animation it's very easy to understand Internal functionality .Great effort and Thanks

Very clear explanation,good that you discussed the enhancements for hashmap in Java 8.

Best tutorial i have ever seen about Hash Map

Thank you very much for this wonderful piece of work. Now certainly I got an idea of how exactly Hashmap works internally.Gonna check the internal activities of put, get and hash in jdk 8 also. Keep the knowledge flowing. :)

Excellent, the animation is Outstanding, great job

One of the best explanation of HashMap

very well explained. Thanks for the video!!