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

Рет қаралды 1,015,177

9 жыл бұрын

How does java hashmap work ? HashMap is one of the most popular java.util data structures.
Its one of the associative array implementations, here I have explained its internals in simple terms using an animation. Java8 adds a bit of enhancement to HashMap by using a balanced tree when there is too much has collisions. I have covered that as well.
Please leave your comments if you liked this. Also, subscribe to the channel for updates on similar topics.
#java8 #hashmap #hashcode #java #javaprogramming #javainstitute #javascript #javatutorial #array #beginners #beginner #study #learnjava #learning #fypシ #fypシ゚viral #trending #tutorial

Пікірлер: 1 000

@RickGladwin 4 жыл бұрын

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

@manishsoni7689 3 жыл бұрын

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?

@sent2anil 8 жыл бұрын

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

@shyamalmunshi 8 жыл бұрын

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

@madhugali 8 жыл бұрын

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

@areyoucerealtube 7 жыл бұрын

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!!

@VinodKumar-ng3kc 5 жыл бұрын

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

@javatmz 5 жыл бұрын

:) right

@ranjithramachandran5928 9 жыл бұрын

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

@chilltouchng 8 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 7 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

@condor1016 8 жыл бұрын

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.

8 жыл бұрын

Excellent job @Ranjith ramachandran! Keep doing it!

@saruncse85 7 жыл бұрын

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

@mirodma 8 жыл бұрын

Amazing approach!! Thanks a lot worked like a charm!!!

@yuyuejiang3278 8 жыл бұрын

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????

@SagarAnkitaUpdates 4 жыл бұрын

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

@ronak212 6 жыл бұрын

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

@jackfarah7494 2 жыл бұрын

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 KZfaq!

@RiteshPuj 8 жыл бұрын

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

@harshavardhan7 7 жыл бұрын

Dude more videos please :) You are awesome :)

@nsarvesh1012 8 жыл бұрын

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

@bikaspatro3329 8 жыл бұрын

Excellent demonstration of HashMap implementation!!

@nabinsaud4656 3 жыл бұрын

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

@shadabsheikh51 8 жыл бұрын

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

@alenka7891 6 жыл бұрын

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

@MikeAetherial 8 жыл бұрын

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

@naveedhassan7399 3 жыл бұрын

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 7 ай бұрын

both hashcode() and equals()

@RagPeddabudi 8 жыл бұрын

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

@ginny5967 3 жыл бұрын

😭

@ginny5967 3 жыл бұрын

@RagPeddabudi 3 жыл бұрын

@@ginny5967 watzup buddy ?

@RagPeddabudi 3 жыл бұрын

@@ginny5967 wat made u cry

@prakashpk6311 5 жыл бұрын

Simply perfect ! Awesome explanation

@gnanasekaranebinezar7199 5 жыл бұрын

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!!!👏

@daikhostephen7288 6 жыл бұрын

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.

@yogeshvbk 8 жыл бұрын

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)

@jiezou7297 8 жыл бұрын

Thank you very much for the work. Explanation is clear and animation is very good!

@jinliu5928 8 жыл бұрын

Very good video! Thank you for your explanation.

@vincentkimt 8 жыл бұрын

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 6 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_ 6 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.

@atulyadav21j 7 жыл бұрын

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. :-)

@gauravsahu90 8 жыл бұрын

Very nicely Explained..Kudos to you (Y)

@RakeshGajjar 9 жыл бұрын

Thanks man! I just learnt something from you! Please keep up the good work.

@jonkc3635 7 жыл бұрын

Your face is in the way of the slides. lol

@chaitu2037 8 жыл бұрын

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 6 жыл бұрын

lol

@ahmetemreboyaci 6 жыл бұрын

well that's ungrateful

@mandy1339 5 жыл бұрын

Thank you!! Excellent video

@FlexerPivot 5 жыл бұрын

Amazing, thank you for this bro.

@sangitdhanani2137 8 жыл бұрын

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

@bashachand8590 5 жыл бұрын

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

@rahulpatil8372 8 жыл бұрын

Very well explained, now i can easily visualize the Hashmap structure and the way how Key-Value stores. Thanks a lot :)

@taoufik.jabbari 7 жыл бұрын

This is the best tutorial i've ever seen for understanding HashMap thanks a lot ! From Morocco

@arvindaggarwal 8 жыл бұрын

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......

@srikanthvalluri1956 8 жыл бұрын

very well explained .. Thanks for sharing!

@rohitmanchanda8412 6 жыл бұрын

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

@kalyanhr 6 жыл бұрын

very well explained. Thanks for the video!!

@DeepakPandey-lz3hy 8 жыл бұрын

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

@clyt9636 7 жыл бұрын

so well explained!!! implementation details and the class heirarchy in just 15 minutes! You're a great teacher

@anuraag3103 6 жыл бұрын

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

@ashrafs965 4 жыл бұрын

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.

@shikher123yo 8 жыл бұрын

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

@chanakakasun9468 4 жыл бұрын

Recommended video Simply explain how it happens well done

@KousikPaul 8 жыл бұрын

Just Awesome..

@timadeshola 7 жыл бұрын

Nice video, very engaging and loaded. Kuddos

@etofok 7 жыл бұрын

thanks, amazing presentation

@huynhmanhhoang5131 7 жыл бұрын

Great! Today I realize that I misunderstand many things. Thank's.

@InnerInvocaction 8 жыл бұрын

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

@mukulanand181 8 жыл бұрын

Awesome!! Really enjoyed watching it so much! Thank you!

@njavier85 5 жыл бұрын

Great video, this is the best video Ive seen explainig how hashmap works, thanks!!!!

@zcarla3 5 жыл бұрын

Loved this explanation!! thank you

@TheN0odles 8 жыл бұрын

Excellent. Thanks for posting.

@ssbabu78 7 жыл бұрын

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

@Stoic623 5 жыл бұрын

Thanks for sharing knowledge It helped me to understand.

@ravisahu3395 8 жыл бұрын

Great explanation about hashing and collisions...

@barrettkepler7618 2 жыл бұрын

HashMaps finally demystified. Thank you very much

@sivakrishnat5471 2 жыл бұрын

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

@user-ju1qd9ek2m 6 жыл бұрын

awesome explain about HashMap

@raazeev1 6 жыл бұрын

The animations help remember things.. Kudos...!! Thanks

@rs6262 6 жыл бұрын

Nice presentation with animation. Thank you...

@maximshen3078 8 жыл бұрын

Best HashMap explanation and animation !

@Jithu0013 4 жыл бұрын

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

@priyankabakshi9765 8 жыл бұрын

Good Explanation..

@dillipkumarnayak786 7 жыл бұрын

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

@amolk4339 8 жыл бұрын

Thank you Ranjith. Appreciate your efforts. This definitely going to make difference to learners... Great job!

@prasant222 8 жыл бұрын

superb explanation thanxx

@senthilkumaravel8305 7 жыл бұрын

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

@nishikanttayade7446 6 жыл бұрын

this is THE BEST EXPLANATION of HashMap...thanks

@rajendrakumar2011 3 жыл бұрын

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

@venkatadhanaraju3214 4 жыл бұрын

Good tutorial for hash map implementaion

@reenalparmar540 6 жыл бұрын

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

@irynasherepot9882 4 жыл бұрын

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

@praveen2hearts 8 жыл бұрын

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

@Me-nk5ic 8 жыл бұрын

Thanks for the great explanation and great work!!

@thirudoddi8485 5 жыл бұрын

Nice Presentation of the Map concepts!

@vipindixitvipin 8 жыл бұрын

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

@momodoufatty3315 5 жыл бұрын

Amazing tutorial. Super easy to understand. Thanks.

@cbennett52 8 жыл бұрын

Thanks for an awesome demonstration and your dedication in making these videos!

@sandeepsingh-de4fg 4 жыл бұрын

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

@jqyang9406 7 жыл бұрын

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!!

@dmytromelnychuk1909 8 жыл бұрын

Its the best video about HashMap!

@ArdhenduShekharSingh1508 8 жыл бұрын

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.

@AmbujRajput 6 жыл бұрын

One of the best explanation of HashMap

@shashankpaliwal6859 8 жыл бұрын

Excellent bro, keep sesame videos like this flowing, best tutorial on the subject

@sonammittal6723 4 жыл бұрын

Best tutorial for understanding HashMap. Thanks a lot !

@popatkalushe1261 4 жыл бұрын

Thanks a lot, i was really afraid and bit confused about this concept , finally I found this explanation and I'm really so happy.

@shivanandkohalli9301 7 жыл бұрын

Very clear explanation. Thank you.

@praveen530y 8 жыл бұрын

Nice Explanation...

@MBadAtGuitar 8 жыл бұрын

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. :)