Great video! One addition to the last question on implementation of HashMap Since Java 8, once a threshold limit is reached for the number of linked list elements added at a particular node, the linked list is re-ordered to a binary tree to implement faster search for collision cases.
This is a awesome 'Ready Reckoner'. I watched this and all are explained clear and to the point. This is great effort by the creator. Please make more topics and please make more videos. I totally understood the points. All the very best team 👍👏 With Regards, Prakash Karuppusamy
Thanks for wonderful comment kathiravan. you might not know this but you made our day and all the efforts we did now turned meaningful bcz of such nice words🙏🙏. We , team code decode is grateful 🙏🙏. keep learning Kathiravan, you will surely land at your dream place really soon. all the best 👍👍👍👍
Hello Ma'am, I have learnt a lot from your channel thank you so much. I have one doubt here that the linked list does not support index based search but it has a get method through which the element is at a specific position?
why java inventors not provided a new overloaded version of add(k,v) which can take two parameters key -value so that MAP interface can also extends Collection interface why there is separate put(k,v) I think the problem would have been solved just by adding one overloaded method add(k,v) pl correct me if I am incorrect
from Java 8, the linked lists are dynamically replaced with balanced binary search trees in collision resolution after the number of collisions in a given bucket location exceed a certain threshold. This change offers a performance boost, since, in the case of a collision, storage and retrieval happen in O(log n).
For others who are interested in that particular topic, the threshold by default is 8 as far as I remember. :) So "after" 8 nodes, LinkedList is being switched to Tree Balance Structure.
Also there is a change in how we store data, initially it was in linked list but now it's red black tree, that also only when the list reaches a threshold then it is converted to tree. A detailed video on that is already on the channel
@@CodeDecode now it uses a CAS (Compare-And-Swap) mechanism combined with finer-grained locking at the bucket level, which reduces contention significantly. Now each bucket (hash entry) can be locked individually for updates, and read operations don’t require locking at all in most cases.
In case of hash collision it also uses equals method to check if key is same. If it is same then it updates the value. Otherwise, new node is inserted.
Hi,As you mentioned, Hashset simply implements Hashtable. It means Hashtable is an interface. But hashtable is class, right? Can you please comment on this?
" Implemented " by this i didn't mean inheritance . I meant how we code it. It means in real time we implement set using hash table. Means it's backed by hash map/ hash table . Sorry for your confusion. Implemented is a term used in both English language and in technical terms
Really a nice approach to make understand the topic. Just one request, plz add some behavioral questions related to collection as interviewer can ask that also.
You mentioned that put method of map just append the node if hash is collision, i don't think so, can you give some references of it, I think if hash is same then it's call equal method and if same key found with equal contain then it's override the value. You can check it via override equal and hashcode(just print something on first line of override version of equal and hashcode) for custom object and just put that object in map, it will call first hashcode, if hashcode is same it will call equal
If you have heard right I have said "another key has same index 0" at 24:12 . Another key can't qualify equals condition. Right? I was expecting you to know that hash code can't have duplicate keys. It will obviously replace the value. The concept I was telling was for different key having same index. Please listen carefully.
thanks for all the tricky quaetions, please explain the HashMap with some examples and this is very short. because i was understanding this only theoretically but havent't implemented. bit more explanation on hash map.. it also talks about the equals() and hashCode() contract..
Code Decode, Your playlist is not coorectly organised, can you please revisit the playlist and reorder it. Like Java 8 Interview Questions, Java Interview Questions and Spring Interview Question.
6:50 Hashtable isn't implemented Hashset, it's "Hash Table" in the code of Hashmap. please check and correct. I got confused when I watched first. If i interpreted wrongly, Please let me know your thoughts.
Hi.. Your videos are the best. You explain so well. Thanks a ton for your efforts. One request.. can you please make a video on how time complexity works in collection?. It would be a great help. Thanks in advance. 🙂
Remembering all concepts of collection fw is just small part of core java , and even if we learn all concept of core java then-recent JD's says you have nothing to do with core java if you don't know the FW such as hibernate or spring ... Ok you don't have knowledge of Database so you are Rejected.
Hi palak, that's so true that now a days job descriptions do require all such stuffs. Keeping this in mind next video I will put on advanced Java interview questions and then will plan for sqls and databases too. I m already in IT sector and have cleared a lot of interviews and with experience i can say this that there is always one job which is best fit for you. Just keep looking and you will for sure end up at the right place at the right time. Just keep patience and keep studying because working in IT sector is totally different and cracking an interview in IT sector is completely different thing.
I went through this whole video and I cannot find the place where I have said it in opposite way. Please let me know where did you find this. Thanks in advance 👍
Thanks for the video. It's really helpful for interview preparation. One small doubt I have in 6:57 you said hashset internally implements hashtable and one null value can contain. But hashtable doesn't contain any null key and null value.. Please explain and correct me.
This is my first ever TH-cam comment. I just logged in to youtube so that I can comment on your video. You are awesome. Very well explained, very well organised. Keep it up. No nonsense videos. I am preparing for my interviews using your videos only. Pls countinue uploading many such videos.
Apologies for inconvenience. We cant fake british accent. It is what it is. No faking. But really sorry that this accent is not understood by people outside. We will try to put translators if TH-cam supports. In which accent u need the sound??
@@CodeDecode In English, as a matter of fact you guys have the most knowledge in the field, people like me look up to you. Just a suggestion - add subtitles to your videos,this will majorly improve your content. No hard feelings you are doing great, keep on improving.
Thanks for the valuable feedback though. We are glad you are helping us to improve🙂🙂need some more of your inputs and time👍🙂kindly help us with some more inputs for better understanding the issue
when i have a key object, lets pretend i am putting it into hashMap, hashcode is generated and putted into hash place, by hash method, is hascode and hash the same thing or i am missing something?
@@CodeDecode by hash bucket you mean the table which is created when i am putting something into the map? then no, i am curious is it working like this: 1. i am putting something into the hashmap 2.table has been created, on the key value hash method is invoked and inside this method hashCode method is invoked (on the result of hashCode method there is some binary operation and we get the result ) 3.this result is used to compute the index etc etc am i right or i am missing something? thank you for answer :D
Question: If the key of Hashmap is Immutable Object(properly create by developer with no mistake or let's say it's String class object) then do we need to override hashcode() and equals()? Or having immutable field as key solves the problem of overriding hashcode() and equals()?
It uses the hashCode() method from Object class. But it's not a good practice beacuse it may effect in equals method returning true for two unequal objects.
In HashTable, we can store the Null values. In the video, you are saying it can not store either null keys or values. import java.util.Hashtable; public class HashTableExample { public static void main(String[] args) { Hashtable ht = new Hashtable(); ht.put(1, "One"); ht.put(2, null); ht.put(3, "Three"); ht.put(4, null); System.out.println(ht); String value = ht.get(2); System.out.println("Value of key 2 is: " + value); } } ======================= Output {4=null, 3=Three, 2=null, 1=One} Value of key 2 is: null
public class LinkedListDemo { public static void main(String[] args) { LinkedList values = new LinkedList(); values.add("Prashanth"); // Integer v=new Integer(4) values.add("Anup"); values.add("Vicky"); values.add("Mahi");
System.out.println("Random Access " +values.get(2)); Iterator it = values.iterator(); while (it.hasNext()) { System.out.println(it.next()); } } } Output : Random Access Vicky Prashanth Anup Vicky Mahi Linked list is allowing me to do random access of elements with index....Am i missing something ...just for understanding im asking
Thanks for the awesome video. However, 18:40 you mentioned HashMap is slower as compared to its respective concurrent counterparts. But that's not true as HashMap is non-synchronized faster. Please correct me if I am wrong
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It helped me in my interview preparation.. thanks
Hope you get all your interviews cleared. All the the best 🤟
@@CodeDecode aa
Kuthe rahto bhau tu? Do u want to take live instructor led classes? I have over 5 years of experience in corporate.
@@realnileshpawar how do i contact u?.
Yes
Though I knew about the framework completely, I had an issue explaining it in an organized way, you are just awesome!
Thanks 👍
Great video! One addition to the last question on implementation of HashMap
Since Java 8, once a threshold limit is reached for the number of linked list elements added at a particular node, the linked list is re-ordered to a binary tree to implement faster search for collision cases.
Thanks for the info
Binary but Binary Search Tree right?
@@JenilCalcuttawala red black tree
Iterable you missed in the beginning
Exactly
Please make a video for Spring interview questions as well..
Sure will do that soon
Code Decode anyway the way you explain is just wow 🤗🤗
thanks :) 👍
This is a awesome 'Ready Reckoner'. I watched this and all are explained clear and to the point. This is great effort by the creator. Please make more topics and please make more videos. I totally understood the points. All the very best team 👍👏
With Regards,
Prakash Karuppusamy
Thanks for the nice words Prakash. We will sure make more videos like this ....
your phone vibrates in almost all of your videos. thats very nice :-). it's not a complaint, take it as a compliment
we fixed this issue in new videos. Thanks 👍👍😊😊
You forgot LinkedHashMap...
Beautiful Effort.IT Field will remember your name forever.
Thanks for wonderful comment kathiravan. you might not know this but you made our day and all the efforts we did now turned meaningful bcz of such nice words🙏🙏. We , team code decode is grateful 🙏🙏. keep learning Kathiravan, you will surely land at your dream place really soon. all the best 👍👍👍👍
4:42 small correction, I think Linkedlist do allow index base search
Yeah is there any pdf for these video....pls let me know if possible
Seriously very great explanation ❤️
Thanks a lot 🙂🙂👍👍
Hi medam,
You have any material like these vieeos
very nice but need more questions from collections with demonistration
Sure we will create soon
Hello Ma'am, I have learnt a lot from your channel thank you so much. I have one doubt here that the linked list does not support index based search but it has a get method through which the element is at a specific position?
Pleasr create more tricky questions on collections
sure sreeja we will create soon
Nice work...one mistake is map interface doesnt extends(not implement) Collection interface
5 lakh 48 thousand + views
Congrats 🎉🎉🎉
Thanks Rishi for your constant support
why java inventors not provided a new overloaded version of add(k,v) which can take two parameters
key -value so that MAP interface can also extends Collection interface
why there is separate put(k,v) I think the problem would have been solved just by adding one overloaded method add(k,v) pl correct me if I am incorrect
Collection interface
is not Root interface of Collection Framework due to Map
Mam you forgot navigable set and navigable map interface
We will cover that in second part
Palindrome program and prime number program explanation I need
Here missed linked hash map concept
java.lang
Interface Iterable is root Interface or collection interface is root interface?
Iterable
iterable
@@avinashwagh7761 Iterable is an interface it should start with I in uppercase
from Java 8, the linked lists are dynamically replaced with balanced binary search trees in collision resolution after the number of collisions in a given bucket location exceed a certain threshold.
This change offers a performance boost, since, in the case of a collision, storage and retrieval happen in O(log n).
Yes we have covered that in latest videos I. E. top interview questions 👍👍. Thanks
For others who are interested in that particular topic, the threshold by default is 8 as far as I remember. :) So "after" 8 nodes, LinkedList is being switched to Tree Balance Structure.
PLEASE UPDATE YOUR CONTENT !!! SEGMENT BASED LOCKING IS REPLACED WITH NEWER DATA STRUCTURES AFTER JAVA 8 !!!
WHAT IS THAT NEW DATA STRUCTURE? CAN YOU PLEASE LET THE COMMUNITY KNOW?
Also there is a change in how we store data, initially it was in linked list but now it's red black tree, that also only when the list reaches a threshold then it is converted to tree.
A detailed video on that is already on the channel
@@CodeDecode now it uses a CAS (Compare-And-Swap) mechanism combined with finer-grained locking at the bucket level, which reduces contention significantly. Now each bucket (hash entry) can be locked individually for updates, and read operations don’t require locking at all in most cases.
Read operation never needed a lock !! Only write operation can cause race condition !!
Can you please explain fail fast and fail safe by codes?
sure akash we will plan and make video on it soon.
Content is really usefull mam! If possible can you attach ppt document also with the video. It would help for quick recap
Time: 18:50. HashMap is not synchronized. maybe HashTable ?
Hash table is synchronized. Did we say it wrong??
Hi. Pls check video on duration -18:50. You wrote syncronized collection … HashMap
18:44 Madam i think you are referring to Hashtable(thread-safe).....But by mistake it's written HashMap in this note.
Please make another video(part2)on collections tricky questions and include concepts like internal working of hash set
th-cam.com/play/PLyHJZXNdCXsfqAkteaQ6JfZ_IHvxX-Hj3.html
I don't get it. There is get method in Linkedlist class. I have heard the same thing in multiple videos. Is it added recently.
In case of hash collision it also uses equals method to check if key is same. If it is same then it updates the value. Otherwise, new node is inserted.
and then Indians apply for Senior Java positions in the US :-)
Great Explanation!!!
One more point: Hashtable doesn’t extend Hashmap.
It extends Dictionary Class.
👍👍
Hi,As you mentioned, Hashset simply implements Hashtable. It means Hashtable is an interface. But hashtable is class, right? Can you please comment on this?
" Implemented " by this i didn't mean inheritance . I meant how we code it. It means in real time we implement set using hash table. Means it's backed by hash map/ hash table . Sorry for your confusion. Implemented is a term used in both English language and in technical terms
its very nice ad helpful.
Thanks Sonali 👍
@codedecode NavigableSet & NavigableMap interfaces are missed
@13:45 can't agree on that point. add can take an Entry , which is key and value. so should be ok isnt??
but index based search is possible in linkedlist contradictory to what you depicted.
Some correction need in the video content
Queue - perform insertion and deletion at front
priority Queue - lower the number means higher the priority
Everything explained to the point!! Thank you for making great videos
Thanks Savita 👍
Very informative and quick to brush up collection framework with examples.
Thanks Robin 🙂👍
Such helpful content and appreciate your hardwork Thank you mam!!
Thanks Manoj 🙂👍
very informative Thanks
Glad you found it helpful😊
Informative ++
Thanks
Hashmap non synchronised
Yeah it's not. Hash table is
Really a nice approach to make understand the topic. Just one request, plz add some behavioral questions related to collection as interviewer can ask that also.
You mentioned that put method of map just append the node if hash is collision, i don't think so, can you give some references of it, I think if hash is same then it's call equal method and if same key found with equal contain then it's override the value. You can check it via override equal and hashcode(just print something on first line of override version of equal and hashcode) for custom object and just put that object in map, it will call first hashcode, if hashcode is same it will call equal
If you have heard right I have said "another key has same index 0" at 24:12 .
Another key can't qualify equals condition. Right?
I was expecting you to know that hash code can't have duplicate keys. It will obviously replace the value. The concept I was telling was for different key having same index. Please listen carefully.
Very good explanation of Internal working of hashmap. Liked it.
Thanks
thanks for all the tricky quaetions, please explain the HashMap with some examples and this is very short. because i was understanding this only theoretically but havent't implemented. bit more explanation on hash map.. it also talks about the equals() and hashCode() contract..
Hi Venkat
These are only interview questions. Will create tutorial for this very soon 👍👍
@@CodeDecode sure, thanks
Superbbb...! your explanation skills are just awesome....
and ur voice is adorable as well. thanks for this questions set it will be really helpful
Thanks Sagar 🙂🙂
Thanks a lot.. The best Collection summary available on YT.
is hashmap is synchronized ?
Nope
Code Decode, Your playlist is not coorectly organised, can you please revisit the playlist and reorder it. Like Java 8 Interview Questions, Java Interview Questions and Spring Interview Question.
Ok sure
Collection interface also extend Iterable interface which is root. Please confirm this one.
Yes it does.
6:50 Hashtable isn't implemented Hashset, it's "Hash Table" in the code of Hashmap. please check and correct.
I got confused when I watched first.
If i interpreted wrongly, Please let me know your thoughts.
Internally hash map uses hash table. Hash set internally uses hash map. So indirectly hash set uses hash table .
Your voice is too sweet mam
Thanks
Hi , I'm stucked in one problem statement where I have to use collection map with duplicate keys can you help me in that
Multimap multimap = ArrayListMultimap.create();
multimap.put(1, "A");
multimap.put(1, "B");
multimap.put(1, "C");
multimap.put(1, "A");
multimap.put(2, "A");
multimap.put(2, "B");
multimap.put(2, "C");
multimap.put(3, "A");
System.out.println(multimap.get(1));
System.out.println(multimap.get(2));
System.out.println(multimap.get(3));
Output is:
[A,B,C,A]
[A,B,C]
[A]
can you plz create a video to show demo about fail-fast and fail-safe ?
Sure we will create separate video on that
Thank you, nice explanation of all collections, mostly I like internal working of hash map, got the more clarity….
th-cam.com/video/7k0VYHuUF6g/w-d-xo.html
Hi.. Your videos are the best. You explain so well. Thanks a ton for your efforts. One request.. can you please make a video on how time complexity works in collection?. It would be a great help. Thanks in advance. 🙂
The time complexity of a collection is the amount of time it takes to perform an operation on the collection
Remembering all concepts of collection fw is just small part of core java , and even if we learn all concept of core java then-recent JD's says you have nothing to do with core java if you don't know the FW such as hibernate or spring ... Ok you don't have knowledge of Database so you are Rejected.
Hi palak, that's so true that now a days job descriptions do require all such stuffs. Keeping this in mind next video I will put on advanced Java interview questions and then will plan for sqls and databases too.
I m already in IT sector and have cleared a lot of interviews and with experience i can say this that there is always one job which is best fit for you. Just keep looking and you will for sure end up at the right place at the right time.
Just keep patience and keep studying because working in IT sector is totally different and cracking an interview in IT sector is completely different thing.
Forget spring and hibernate they now want person with microservices knowledge with devops tools. I am so frustrated due to this.
We will cover micro services, Eureka, elastic search, rest API , CD ci pipeline, docker every thing slowly
Hashmap is not synchronised hashtable is synchronised..i guess you wanted to say hashtable there
Hey Nikita there must be a confusion here. As said at 11:44 minute - hash map is non synchronised.
And that 12:12 we have discussed that hash table is synchronised.
I went through this whole video and I cannot find the place where I have said it in opposite way. Please let me know where did you find this. Thanks in advance 👍
@@CodeDecode 18:44
There I was marking on screen. It's correctly said. Markings might be over lapped that's why you are not able to see my cursor.
Thanks for the video. It's really helpful for interview preparation. One small doubt I have in 6:57 you said hashset internally implements hashtable and one null value can contain. But hashtable doesn't contain any null key and null value.. Please explain and correct me.
The way you explaining each topic is awesome.
Thank you for the amazing video.
Thanks for the nice words.....
This is my first ever TH-cam comment. I just logged in to youtube so that I can comment on your video.
You are awesome. Very well explained, very well organised. Keep it up. No nonsense videos. I am preparing for my interviews using your videos only. Pls countinue uploading many such videos.
Thanks Pallavi 🙂👍
Yes this is literally most asked and top questions. Thanks.
Thanks
It enhanced my knowledge for sure. Thanks.
thank you madem very good explanation 👌👌👌🙏
You are welcome
Beautiful voice.. 😅 and the content is so good that you almost covered main topics that can consume most of the time at institutes.
Thanks Ravi 🙂🙂
Thank u so much,your way of explaining concepts are wonderful.I am feeling so confident in Java after watching your interview questions.
Thanks Shivani 👍👍. Keep learning keep shining ⭐✨⭐✨
Please add more question which can be asked for 7 yrs experienced
Sure we are planning to do that soon.....
Awesome video for java collections 💯💯💯
Thanks sakshi 👍
Internal of hashset and mock interview preparation
th-cam.com/video/7k0VYHuUF6g/w-d-xo.html
Here u go
Linked hashmap
👍👍
Now with recent release treeset is being used in case of collision.
th-cam.com/video/7k0VYHuUF6g/w-d-xo.html
Can you please make videos only on hashmap? All the interview questions related to hashmap?
Sure 👍👍
an image with all the information would be great
Please continue and create video for internal working of hashset as well.
Sure👍👍
I was hoping it was in English not in Hinglish.
Apologies for inconvenience. We cant fake british accent. It is what it is. No faking. But really sorry that this accent is not understood by people outside. We will try to put translators if TH-cam supports. In which accent u need the sound??
@@CodeDecode In English, as a matter of fact you guys have the most knowledge in the field, people like me look up to you. Just a suggestion - add subtitles to your videos,this will majorly improve your content. No hard feelings you are doing great, keep on improving.
Hey man we can see subtitles already there in this video. And they are translating properly too. Are we on same page? Are we missing any thing here
Thanks for the valuable feedback though. We are glad you are helping us to improve🙂🙂need some more of your inputs and time👍🙂kindly help us with some more inputs for better understanding the issue
550K views🎉
😊😊🙏 Thanks Rishi for being there with us since so long
when i have a key object, lets pretend i am putting it into hashMap, hashcode is generated and putted into hash place, by hash method, is hascode and hash the same thing or i am missing something?
Are you confused between hash code and hash bucket
@@CodeDecode by hash bucket you mean the table which is created when i am putting something into the map? then no, i am curious is it working like this:
1. i am putting something into the hashmap
2.table has been created, on the key value hash method is invoked and inside this method hashCode method is invoked (on the result of hashCode method there is some binary operation and we get the result )
3.this result is used to compute the index
etc etc
am i right or i am missing something?
thank you for answer :D
Question: If the key of Hashmap is Immutable Object(properly create by developer with no mistake or let's say it's String class object) then do we need to override hashcode() and equals()? Or having immutable field as key solves the problem of overriding hashcode() and equals()?
Yes you have to.
Immutability does not make sure that your equal objects are stored at same bucket location. Hash code does. Interviewer is just trying to trick you.
@@CodeDecode thank you!
Very clear explanation.. and provide example code 👍👍👍👍
Thanks Siva 👍👍
you have missed linked hash map
Excellent videos, Thank you so much!
Thanks Nidhi 🙂👍
Can u also explain what happens when we only implement equals metho and not hash code method..?
It uses the hashCode() method from Object class. But it's not a good practice beacuse it may effect in equals method returning true for two unequal objects.
In HashTable, we can store the Null values. In the video, you are saying it can not store either null keys or values. import java.util.Hashtable;
public class HashTableExample {
public static void main(String[] args) {
Hashtable ht = new Hashtable();
ht.put(1, "One");
ht.put(2, null);
ht.put(3, "Three");
ht.put(4, null);
System.out.println(ht);
String value = ht.get(2);
System.out.println("Value of key 2 is: " + value);
}
}
=======================
Output
{4=null, 3=Three, 2=null, 1=One}
Value of key 2 is: null
SortedSet uses Comparator(Comparator
Very good. Explanation. Thank You 😊
Thanks 🙏
public class LinkedListDemo {
public static void main(String[] args) {
LinkedList values = new LinkedList();
values.add("Prashanth"); // Integer v=new Integer(4)
values.add("Anup");
values.add("Vicky");
values.add("Mahi");
System.out.println("Random Access " +values.get(2));
Iterator it = values.iterator();
while (it.hasNext()) {
System.out.println(it.next());
}
}
}
Output :
Random Access Vicky
Prashanth
Anup
Vicky
Mahi
Linked list is allowing me to do random access of elements with index....Am i missing something ...just for understanding im asking
Thanks 🎉
🙂👍
Thanks for wonderful explanation 🤝
You are welcome
Thanks for the awesome video. However, 18:40 you mentioned HashMap is slower as compared to its respective concurrent counterparts. But that's not true as HashMap is non-synchronized faster. Please correct me if I am wrong
very nicely explained... eagerly waiting for Multi-threading concepts.. once again good job!
Thanks .......
I have read theory before but confused after this video cleared all doubts about Hashmap,, thanks a lot
We are glad to know that this helps Ganesh 🙏👍
Hello Akka, need practical example...
Sure will create second part. In that will give you live demos. Is that what you want ?
@@CodeDecode okay, please explain with code, then it will make more understandable to learners and learned people
Sure will do that in second part 👍
yes i would love to see internal working of hashSet
th-cam.com/video/7k0VYHuUF6g/w-d-xo.html
Nice video keep it up 👍
Thanks ☺️