How HashMap works in Java? With Animation!! whats new in java8 tutorial

[@RickGladwin]

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]

Thanks Rick

[@MuzicalMelody]

How to get the hash value

[@yaruiwu7408]

This is just wonderful

[@balajikoc1429]

Thanks Rick

[@adarsh6750]

Thanks rick

[@manishsoni7689]

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]

This point is very necessary to complete this good video.

[@PavanKumar-yj8fu]

Very good point, thanks

[@ArkAngelHFB]

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

[@dmitrikonnov922]

@@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]

@@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?

[@sent2anil]

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

[@madhugali]

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]

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]

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]

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

[@v0nnyboy]

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

[@ayushman_sr]

this was important part... yet nit covered

[@shyamalmunshi]

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

[@anuraag3103]

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

[@condor1016]

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.

[@barrettkepler7618]

HashMaps finally demystified. Thank you very much

[@VinodKumar-ng3kc]

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

[@javatmz]

:) right

[@jackfarah7494]

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 KZbin!

[@areyoucerealtube]

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!!

[@sandeepsingh-de4fg]

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

[@nabinsaud4656]

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

[@nishikanttayade7446]

this is THE BEST EXPLANATION of HashMap...thanks

[@ranjithramachandran5928]

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

[@chilltouchng]

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

[@ChandrakanthReddySoodiReddy]

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

[@atulkumar-hm6yo]

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

[@satyaprakashnayak1363]

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

[@kinjalthehero]

Thank you

[@sivakrishnat5471]

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

[@saruncse85]

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

[@gagangupta1255]

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

[@SagarAnkitaUpdates]

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

[@rajendrakumar2011]

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

[@RagPeddabudi]

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

[@ginny5967]

😭

[@ginny5967]

R

[@RagPeddabudi]

@@ginny5967 watzup buddy ?

[@RagPeddabudi]

@@ginny5967 wat made u cry

[@benjaminsinanovic4123]

Best explanation from all videos I looked on yt.

[@naveedhassan7399]

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]

Good one brother

[@vyshnavramesh9305]

both hashcode() and equals()

[@irynasherepot9882]

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

[@yuyuejiang3278]

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

[@ranjithramachandran5928]

Thanks!

[@arvind143100]

@@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]

@@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????

[@techiebrat9498]

Awesome explanation .thanks a ton.

[@RiteshPuj]

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

[@scubemovies]

Best tutorial i have ever seen about Hash Map

[@pierryangelo]

Excellent job @Ranjith ramachandran! Keep doing it!

[@jqyang9406]

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!!

[@harshavardhan7]

Dude more videos please :) You are awesome :)

[@chaitanyaasati]

Amazing explaination and animation!! Love it.

[@shadabsheikh51]

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

[@Jithu0013]

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

[@daikhostephen7288]

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

[@sameer_sah]

any references ?

[@sergeyvechkitov221]

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

[@bsaikumarreddy1413]

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

[@cathynest459]

This is the best explanation so far

[@vincentkimt]

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]

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

[@raju5081]

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

[@_Vaibs_]

+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.

[@gnanasekaranebinezar7199]

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!!!👏

[@chaitu2037]

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

[@rhimanshu6288]

true

[@nirmitsrivastava]

true

[@rexroy4037]

yes its kind of disturbing ..

[@shubhamsrivastava5400]

lol

[@ahmetemreboyaci]

well that's ungrateful

[@sonammittal6723]

Best tutorial for understanding HashMap. Thanks a lot !

[@yogeshvbk]

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

[@ranjithramachandran5928]

+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)

[@roxanamoghbel9147]

this is the best explanation on the internet

[@atulyadav21j]

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]

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

[@skullwise]

I had asked the same question. :-)

[@AmbujRajput]

One of the best explanation of HashMap

[@jonkc3635]

Your face is in the way of the slides. lol

[@ssbabu78]

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

[@sangitdhanani2137]

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

[@dhirajchandra778]

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

[@robertsahayakumar5267]

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.

[@shikher123yo]

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

[@djethrak4567]

Best explanation I have seen so far

[@vaibhavjain3610]

The best explanation for hashmap internal working. Thanks man.

[@mathisinav4267]

Excellent, the animation is Outstanding, great job

[@ArdhenduShekharSingh1508]

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.

[@uzoamakamadueke7101]

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

[@ke30_]

Ty so much this is a great explanation

[@ronak212]

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

[@rajajodhani]

So helpful and explained in a very simple way

[@stark469]

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

[@tolibisql]

Best explanation. Perfect

[@reenalparmar540]

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

[@vibhorhadke988]

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

[@satyajeetkumarjha1482]

Really good explanation with the help of animation.

[@AbhijitDixit-ki1oo]

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

[@dmytromelnychuk1909]

Its the best video about HashMap!

[@swamik5935]

Very well explanation of HashMap .

[@amansrivastav9691]

One of the genuine and worthy explanation.

[@KZwai]

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

[@ravisahu3395]

Great explanation about hashing and collisions...

[@SeekerofYab]

You've made this really easy to understand, and your animations are super-helpful. Thanks!

[@ranjithramachandran5928]

+raszelast thanks!

[@maximshen3078]

Best HashMap explanation and animation !

[@rs6262]

Nice presentation with animation. Thank you...

[@pravinghorpade2771]

Very Good explanation and Animation...Thanks

[@radhikagadve]

there cannot be a better explanation than this... thanks :)

[@MrAsgar123]

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

[@dillipkumarnayak786]

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

[@pushpal.r.1096]

Very nice explanation. Thank you Sir.

[@shuvenduoffline]

Nicely explained! Thanks, keep creating !!

[@indurana1835]

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

[@pankajk2928]

This is the best explanation for HashMap. Thanks Ranjith.

[@ziqic3019]

Thanks for the well explained HashMap

[@MikeAetherial]

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

[@bikaspatro3329]

Excellent demonstration of HashMap implementation!!

[@NileshPatil-m9l]

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

[@MadhuCM]

Excellent explanation with animation. great going and thanks.

[@arvindaggarwal]

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......

[@abhilashreddy3853]

Thanks for a clear explanation with visuals.

[@AmitKumar-qh4ow]

Excellent Video on HashMap

[@neetishraj]

Thank you Ranjith, you strike right into the root concepts that clear all doubts that branch out from that root confusion. Thank you sir

[@TheN0odles]

Excellent. Thanks for posting.

[@72seenu]

Very nice explanation Thank you so much .

[@bavanasudheerkumar]

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

[@araveetivenkatesh6942]

Very good explanation.thanku somuch

[@mollamainuddin6485]

awsome tutorial.....thank you very much

[@jathitu]

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.

[@AshishBurnwal]

Best explanation till date... Thanks a lot

[@momodoufatty3315]

Amazing tutorial. Super easy to understand. Thanks.

[@praveen2hearts]

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

[@kishorejosyula6794]

One of the best explanations I have seen!!!!

[@chanakakasun9468]

Recommended video Simply explain how it happens well done