#17 - How HashTable works Internally? HashTable vs HashMap in Java - By Naveen AutomationLabs

In this video, I have explained How HashTable works Internally? HashTable vs HashMap in Java.
It's a very popular interview question in Java if you are going for Java, SDET, Automation profiles.
Full Java Collection Playlist:
• Latest Java Collection...
~~~Subscribe to this channel, and press bell icon to get some interesting videos on Selenium and Automation:
kzbin.info%20Au...
Follow me on my Facebook Page:
/ naveenqtpexpert
Let's join our Automation community for some amazing knowledge sharing and group discussion on Telegram:
t.me/joinchat/COJqZUPB02r5sB7...
Paid courses (Recorded) videos:
naveenautomationlabs.com/reco...
For Java & Selenium - naveenautomationlabs.com/selen...
For API (Manual + Automation) - naveenautomationlabs.com/manua...

[@kavinithees2696]

World's best explanation 👌💯 highlight is you have explained with the debugger mode no one will explain like this. While I'm writing the codes and debugging expanded the hashtable there is an lot of nulls available but now I got to know thes reason. Thanks for your explanation 👍

[@naveenautomationlabs]

Glad that you liked it 🙂

[@shashankjain9704]

Thank you so much for this video. I was studying this topic for many days. Now, finally the internal working got cleared.

[@kumarnavit9355]

Best of all the explanations available over youtube

[@dushyag3303]

Clear explanation.. looked at several sites never understand this clearly Thank you 🙏

[@amitbhattacharya356]

Flawless explanation. Thanks for this video, I liked the way how you have shown with debugger mode on. I am lucky that youtube has suggested me this video.

[@arvindhr.a2315]

First time watching a video with such an explanation, Excellently explained sir ! Thanks Much.

[@seekersofwisdom85]

Its a very good video. I was searching for a good one. Finally. Thanks Man.

[@varunbe09]

Very well explained . Today I attended interview for amazon austin location senior software engineer, and they asked me this question.

[@chetanchoudhary08]

The main thing to explain here was how hashset avoids null keys and how it is synchronized. Other than that it was good

[@user-tr6hy8pr5v]

Wonderful explanation..Thank you so much. Please provide more video's which will be very helpful

[@navdeepupadhyay5984]

Thanks, Naveen for the deep explanation.

[@sagar1691]

Brilliant , Wish every technical topic in any stream have these kind of videos to explain in details... Looking forward to more videos like these.

[@naveenautomationlabs]

Glad you liked it

[@bishalkumarmohanty3782]

Important for Interview..Exceptional

[@ajitbombe5168]

Perfect explanation ! thank you :)

[@vinaysharma530]

Okay sir thank you Your explanation is very good👌

[@akshaysharma2841]

great video. I watched your video on internal working of hastable as well . Seeing the video above, is it safe to say that internally both hashtable and hashmap work similarly with regards to collision as the data entry depends on the hashcode generated and the index being calculated? Would appreciate if you can clear my doubt.

[@velanc902]

Nice one Naveen.Thanks for this video. Waiting for more :).

[@naveenautomationlabs]

more videos will be there. I'll make you guys perfect in Java Collections.

[@letmehink166]

Great videos..In the interviews for the testing automation profile, will they also ask to write the code to show internal working of hashtable or hashmap, or just the concept explaination? Pls reply

[@shruthishru3553]

wonderfully explained..thanks a lot :)

[@ramyaraja9411]

Thanks for this video Naveen.. Well explained..

[@naveenautomationlabs]

My pleasure

[@PrakashPradhan-lo4cv]

wonderful explanation👌👌

[@syedjami4033]

best explanation on the internet

[@moulikavankam]

Hi Naveen, Your videos are too good even for beginners. I have a doubt. In get method, will it use hashcode method or equals method to validate the key? Please clarify.

[@rsundar81]

Good Explaination.. Keep going..

[@ahmadreza7508]

Thank you so much for this video

[@yadneshtakalkar275]

beautifully explained

[@praveenkumaer4502]

Excellent explanation

[@vinayakthorat7231]

Thanks Naveen!

[@shriramnirmal5535]

Very helpful video, I have a small confusion , can hash code be same for two different key values , because even in collision while using get method on same index the hash codes seems different , I am bit confused with the same hash code problem , can you please clarify it

[@anupamasingh7366]

Hi Naveen, do we have threshold value restriction in HashTable also like hashMap ?

[@sn2dk1]

Thank you so much

[@akashsingsarva7110]

Nice work bro.

[@rajeshyadav-cw6vc]

Thank you sir👌🙏

[@karthickg9931]

HI Naveen, Once the threshold is reached the linked list of Hashmap will be converted in to balanced binary tree similarly in Hashtable what is the threshold value and will it change to binary tree here as well, once the threshold is reached? Please clarify on this part. Thanks in advance :-)

[@socialmedia434]

Hi Naveen, Can 2 keys have the same Hashcode? When they have the same index collision occurs. What happens when they have the same Hashcode. also @18:58 when you said peter and Naveen have same Hashcode did u mean they have same index?

[@afrozalam9857]

Hi Naveen, In case of internal implementation of Hashtable and HashMap, is there any difference?

[@nikhiltiwari975]

good one , sir :)

[@subhashreesahoo2233]

Thanks... So important..

[@naveenautomationlabs]

Glad that you liked it.

[@testinginsights-muktasharma]

Hi, can you please check the links in the description box? Looks like those are not working. Please let me know once you update it. I am more interested in knowing api(manual&automation)link please. Thank you!

[@xoda345]

Hi Naveen, between 18.03 to 18.12 you said that in case of collision, hashCode is same but there is no guarantee that it will be same. It can be same or different. Instead of hashCode shouldn't it be index like index should be same during collision?

[@shaleensudhakar8383]

From Java 8 prospective there is change in the working of hash collision. in worst case scenario if all keys generating same hash code then the performance is decreased from O(1) to O(n). to solve this Java 8 replaces linked list(storing same hashcode keys) to binary tree when certain threshold increases.

[@krishanuchakraborty3500]

I don't understand why these beautiful videos of yours are not gaining traction as much as your Whiteboard or Selenium series...

[@naveenautomationlabs]

Most of the people want to learn just Selenium, but not actual programming concepts. That's ok, these videos will always be there for you guys to learn. It will get traction eventually.

[@pratikjain1937]

Nice explained...

[@krishanuchakraborty3500]

@@naveenautomationlabs Thanks for your reply, yes I am sure they will gain traction, quality content always does👍🙏

[@naveenautomationlabs]

@@pratikjain1937 Thank you...:)

[@naveenautomationlabs]

@@krishanuchakraborty3500 Thanks for your words. Keep sharing these videos in your network.

[@RakhiDhavale]

well explained

[@blessyRelatable]

Thanks

[@jyotikoli6006]

Sir hashtable and hashMap both create a linked list internally if there is any collision... So both work same???

[@shashankvishwakarma959]

i have a doubt here while performing get operation, for get("Naveen") we only comapre 'hashValue' or only comapre 'key' ... and .equals is applicable in which scenario ie: for hashValue or for key ... thanks in advance !!

[@pratapjavasingh3239]

One more doubt is related to the fail safe fail fast when my implementation collection classes like hashmap not threads safe then we caught the concurrent modification but if u are taking vector then it's threads safe again we caught the same exception when are performing read and write operation both at a time why

[@gauravvarma6483]

Thanks a lot, Naveen Awesome explanation. I have one doubt. Suppose index 4 has ("India",10) and next time we are trying to add ("India",20) now the same hashcode and the same index will be generated so there is collission. Since it doesn't allow duplicate "India" will have which value 10 or 20? are we using equals() here?

[@naveenautomationlabs]

Duplicate keys won't be accepted. It will take the latest value as 20 on key = india.

[@gauravvarma6483]

@@naveenautomationlabs got it. Thank you so much

[@bogastocksstocks8366]

Can you explain same for ConcurretHashMap and SynchronizedMap. thanks in advance.

[@pratapjavasingh3239]

I have one doubt regarding the garabage collectors respect to the Hashmap so if u taking the weak Hashmap and ur reference variable as a null then garbage eligible for destroying the object as a null refrence but in same case if u taking hashmap then ur unrefrence object not eligible to garabage so here my question is that's why not dominated to respect to the Hashmap same as weakhashmap object

[@socialmedia434]

Hi Naveen @Naveen AutomationLabs can two different keys have the same hashcode. What happends in this case. Kindly explain. Thank you

[@naveenautomationlabs]

Yes it can have the same hashcode for two different keys or objects. It will calculate same index and collision will happen.

[@socialmedia434]

@@naveenautomationlabs Thanks Naveen. Also does the get() method use both hashcode() and equals(key) method to look for the key? or just equals() method to search for the key? Thank you

[@conred1401]

🔥🔥

[@joshbenjamin1100]

I'm not able to see the hash code in intelliJ the way you find it (I think you're in Eclipse); any pointers?

[@bisht173]

What about equals method in case of collision..

[@rithup2420]

I have a question here, we have inserted naveen first and then Peter. So in debug mode I see Peter is inserted first and then naveen is inserted after Peter. How is this possible and explanation pls

[@DurgaShiva7574]

this is a very nice video..but please explain is there any difference in HashMap and Hashtable classes apart from versions of java in which they were included(as the internal working of both of them seems to be same) ..if yes..please explain...also please tell WHY Hashtable doesn't allow even 1 null key (or value as well),, whereas the hashmap does...????...can anybody please answer to these questions...thanks in advance

[@naveenautomationlabs]

Refer this video: kzbin.info/www/bejne/iYnJpHV6idSXprs

[@rahulbotcha9456]

how did you put naveen key in the 4 index

[@pratapjavasingh3239]

One more doubt same as Hashmap why only one as null key and multiple null value alloweded and this kind of features not available in hashtable and it's possible then explained by use cases

[@VikasSharma-hm6xt]

what is the type of that array segment?

[@akki7949]

It wont store hashcode like it is done in hashMap??

[@akki7949]

It working is same like hashmap. Only difference I found that number of bucket in hashmap is 16 and in hashtable is 11. And formula to calculate index is different.. this is the only difference? Pls reply

[@arvindmd3280]

Yes you are right

[@akki7949]

@@arvindmd3280 thnxxx

[@kumarjadhav6106]

How to resolve hash collision..