How are HashMaps implemented in Java? Internal Working Explained With Code | IMP Interview Question

0:00 - Introduction
0:40 - Contents of the video
1:30 - Why do we need a HashMap data structure?
5:15 - Calculate frequencies using a simple array.
7:50 - Problems with the above approach.
8:50 - Using Bucket Array
11:00 - Introducing Hashing and Hash Function?
13:15 - Compression Function
18:07 - Hash Collision
21:15 - Closed Hashing/Separate Chaining
23:51 - Open Addressing
24:56 - Implementing HashMaps in Java [ CODE]
40:53 - Time Complexity of our Code
43:45 - Rehashing
48:00 - Implementing Rehashing in our code
50:15 - Testing our HashMap
50:34 - Ramping Up.

Tags
#hashmap
#java #javaprogramming #riddhiduttajava #javadeveloper #javadevelopment #javatutorial #spring #backenddeveloper #multithreadinginjava #multithreading #concurrency #javaconcurrency#backendwebdevelopment #collections #collectionframework
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[animeshjaiswal]

Hey Ridhi, I watched your Collection Framework and Multithreading videos before 1 week of my interview and I am very happy to tell you that I got selected out of 10 candidates to that company for Java profile. Your teaching style is just so awesome. Please keep on posting new videos brother.

May God give you all the happiness 💝🙏🏻

[shankar]

Excellent explanation without any kind of repetition. Great content on YouTube.

[Anilkumar-reddy]

Finally, Master Java is back on youtube. Good See you

[sounishnath]

❤❤ if you ask me i must day while watching the full video your explanation did not feel like I’m watching via YouTube. ❤❤ i feel like we are directly interacting.


Super Riddhi da ✨. More this type of titbits we need . Kudos

[ketansarode]

Really the best explanation ever on hashmap implementation ❤👍

[TheBikerDude]

Amazing explaining and kudos for your deep knowledge and expertise.

[dayashankarlakhotia]

Good explanation with code much intuitive

[Kavya-]

Worth watching your videos 💯..but shocked to see very less views . Do keep posting more videos on java

[ayushsingh]

It's a good video. Didn't find such content.

[HamzaKhan-wikb]

great video Riddhi, but just to point out the hashcode function does not give the memory address of the object.

[Hitesh-qo]

Hi riddhi it was really great explanation but there is small change in code need to wrap Math.abs(key.hashCode()). there can be negative hashcode and negative numbers will give the error while getting the index of the table(bucket)

[prateek]

I haven't seen any explanation on Hashmap that has this much depth.
But It would have been even better if you discussed the worst case time complexity under high hash collisions would be O(n) in this linked list implementation and it can be reduced to O(log n) using balanced BST.

Can you please discuss in a separate video about this Balanced BST implementation when the treeify_threshold has been crossed ??

[factnoted]

Hi Riddhi,

Can you also talk about why you were not using this keyword to set/update the values. Example this.size=0,

[thimothipalipaka]

1hr back only done this problem using the hashmap. It takes lot of memory size than nested for loop to find number of occurrences of an element . Basically i from non it which one should I prefer space complexity or time complexity to design the alogorothm

[sankarapuvishnuvardhan]

A great explanation Riddhi. Thanks for explaining in such deep, as it is very important to know about load factor and initial capacity. We can also provide a constructor which takes initial capacity and load factor arguments also right? as it's done in the default HashMap class.Again, thanks for your effort

[rohitsriwastav]

Great explanation. I have got a different level of clarity in internal working of Hashmap. But I still have one doubt regarding the reduction in collisions. Suppose, the load factor crossed the threshold and we doubled the bucket array size and rehashing is also done but now also only the bucket index is going to change because of the change in compression function but for the objects which had same bucket index before rehashing, they will still be having the same bucket index just at a different index now.

So, after rehashing, how does Hash fucntion will reduce the collisions??

[SnehansuPradhan]

Sir make a full playlist of spring and spring boot

[accforgame]

I need advice m fresher struggling to get a entry job using java stack
What i want to know is shud i be doing advance topics of java the ones u teach seems little advance or i should stick to core and only practice that

[karanjitsinghrandhawa]

Hi sir currently I am working as a flutter developer in Renault Nissan
And I am preparing more DSA for top product based company can you please tell will my tech stack i.e flutter will be reliable for companies like faang please sir

[kp-cjro]

Your voice is getting resound i thought that was due to your room....can you pls resolve it if possible....