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Exemplary tutorial, as always. Timings + my notes below that might help others: 1:45 An example of how hashmaps can help 2:05 Creating and naming a hashmap 2:40 How to add values to a hashmap using the .put method 3:52 Why you should use a generic and data type for type safety when creating a hashmap + how to add this 4:25 Why you need 'Integer' [i.e. class type] for a hashmap (can't take primitive 'int' type) 5:00 Test print of hashmap (default output displays in set notation) 5:30 Calling a specific value from the hashmap - .get call 5:50 Start of more advanced hashmap functions - user + password example 6:15 Creating a hashmap with specific type for type safety 6:33 How to add users and passwords - .put method 7:32 How to remove elements from a hash map - .remove method 8:08 Check if hashmap contains a specific value - .containsValue 8:42 Difference between Values and Keys in a hashmap using .containsValue and .containsKey method calls 9:23 How to replace a value (password) - .replace method 10:10 Key difference between hashmaps and array lists - hashmaps don't have a specific order whereas array lists have an index 11:00 Simple summary of what a hashmap is

This is actually the best description of HashMaps I have seen yet

This video is awesome. Your english is clear and understandable. I like it 👍

I don't know if you'll see this since it's an older video but you're probably the only programming tutorial KZfaqr that's relatable. The rest of them are super smart and do know what they're talking about (so are you obviously) but for some reason, you admitting that a certain topic or part of a topic confuses you helps me understand the material more when you explain it.

Yes the name itself used to make me think that this HashMap thing is one of the most complicated things in Java. Your tutorial made it look like a piece of cake. :) Thanks! keep up the good work.

For anyone with a python background, hashmaps are the same as dictionaries.

2:00 It's called HashMap because it uses hash key to access values in the background and implements Map interface and extends AbstractMap class. If you would write your custom HashMap it would be array of linked lists. Length of the array would not be equal to number of stored key-value pairs. Instead array stores linked list heads, where each list node has hash key, value and points to next node. Hash key is hash version of the key you inserted. To access the value nodes are iterated until hash key matches.

Best hashmapping tutorial! super easy to understand well delivered! more tutorials to come THANKS! :D

Love your tutorials, so clear and concise! you just get to the point and it just makes sense!

This is so helpful. Your explanations and presentation are perfect.

i have watched too many java channels but i found you is the best the best thing about is you is you start to explain a topic in such a way that nothing more required to learn that perticular topic. please bother upload all the java tutorials like spring mvc swings etc.

So glad to see how your channel has grown over time. You really deserve it!

I was working on a master order assignment where we had to make a map of cookie variety and its numBoxes sold. This video was very helpful since he basically said, here is the assignment. You're gonna need to know Maps. I appreciate the tutorials. Thank you so much.

I loved the names haha "happy" and "fun", thank you so much for your explanation you made easier to understand

for anyone that is wondering, it is called a HashMap because it uses a technique called hashing.

Thank you very much Alex! I was struggling with HashMap for all day, and your video really helped!!

Seriously you taught a semestre worth of studies under 20 min. I thank you. I couldn't figure this out until your video. Please make more videos on data structures. I get your explanations.

I wonder how many people, beside me, who graduated IT thanks to you and John. I appreciate you.

I finally understood, thanks for the video!! Btw the sound of your keyboard is so satisfying😨

Most useful on teaching me hashmaps, Thank you so much!

Thank you for explaining things so well. You make otherwise complicated things sound so easy to understand. Bless you brother!

just as simple as u.thanks.it is a one kind of social work.we need people like u.

In a technical aptitude exams hashing question were asked ..had no idea what hashing was and didn't do well but now it is crisp and clear thanks to u Sir..

Dude, thank you so much for this video! I'm 2 years into a computer science degree program and this is the first explanation of a hash map that has made sense to me!

The UI you created it beautiful!

You make everything so simple. Thanks a lot !

now that's amazing how something so abstract to me has become instantly crystal clear. you are awesome!

This young dude is my favorite tutor in youtube !!

Hello Alex and thank you very much for your videos. They are awesome! For this video in particular, it was not clear to me what are the differences of HashMap and ArrayList, and how too choose which to use. Thank you again!

That keyboard is amazing! Thanks for clearing up hashmaps for me, makes it easier when we get there at school.

the most simplified yet extremely informative tut on hashmap. great work m8 :)

Been studying for my Software Engineering Interview, and these videos are so helpful!

Couldnt imagine a better tutorial out there! Great Video man!

Your Videos are straight to the point , My Coding phobia isn't anymore because of your videos...

Thank you for the video. This covers almost everything for novice learners.

Bro say it’s confusing to him but now I just learn the concept in most simple way. Thank you bro 😂

Its called HashMap because it's a data structure that uses the hash function to generate a mapping of keys and their corresponding values.

Your videos are amazing! Thank you!!! You break down complex things so that I can better understand what's actually going on

thank you for making coding tutorials that arent mind numbing

You are great my son. May God Bless you.I am 48 but steel I am your student. Thank you very much.

This was extremely helpful in helping me understand hashmaps. I wasn't understanding them in lectures but this definitely helped clear things up. Thanks!!!

lovely dialogue delivering, excellent quality of video, concepts told in lay man terms. enjoyed and learnt. keep up the good work Alex. :)

Damn, his Java tutorials are totally understandable, thanks

that's just straight as an arrow. Awesome bro.

I finally understand HashMaps. Thank you so much!

love the teachers who make understanding fun. thank you sir

Wow thank you I was unable to understand hash maps until I stumbled upon your video. Thank you :)

you don't give weird analogies like other youtube videos good work

great tutorial. I understand it alot than my teacher. Thanyou! post more java tutorial

It was originally used in cryptology as method of assigning a key that is generated using a underlying algorithm and thus this key is then used to place the value into a data structure that can be retrieved. From this it was used because the second and most commonly used reason now is to reduce the search time complexity from O(n), O(n^2) and so on; to O(1). The hash value is the return value of the function that used to generate that hash value and is used as the index positioning of the element and hence used as a key

Thank you so much, you're an awesome teacher.

I definitely recommend Alex's video! Easy to understand and follow!

i don't usually write comments but your tutorials are so good and helpful. keep going !

These tutorials are awesome. You make java look so easy. Thanks for these easy tutorials!!

Extremly good explained! Way better then my proffesor! Sure its not advanced, but i at least undertood the basicis of HashMap. Thank you.

You do a great job! Simple and clear! Thank you.

Thanks for taking time to create content that helps me understand Java! Great job!

As usual GREAT! Understanding the concept in 11 minutes :)

pls make a full session on java , your style is best .

You're the best coding tutor!

you explained it effortless

Alex you connect really well with your audience. Also about such subjects, I always used to think that i wont understand.. But after watching my first video, the perception has been changed. Please continue making contents. All the best to you. :)

Ivbeen stressing out over this for days cuz of my final. Learned it conpletely under 12 min just now. Just need some practice and the final is gonna be ez. thanks bud!

My favorite java tutor. if I am not mistaking if u want order you can use TreeMap

You simplified it perfectly.. thank you sir

Best hashmap tutorial ever!

Teaching method really awesome. Wish your good health.

Really good tutorial dude. Finally someone who dont have a crappy mic and a indian accent :D pd : the editing was amazing too!

Hey Alex you're amazing I really love the way you teach...Stay happy 😉

Just like any other concepts, we learn basic of Java and integrate those knowledges to better understand more complex concepts. HashMap is named as it is because it possesses properties of Map and uses hashing logic in organizing and structuring data. Data Structure ✌🏼 Cool vid

thanks a lot i solved the follow program only bcoz of ur help.....FIRST ONE is the one with warning and error code as following......Note: HelloWorld.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details..........SECOND ONE is correct one... FIRST CODE WITH WARNING import java.util.*; public class HelloWorld { public static void main(String[] args) { HashMap map = new HashMap();/"line with warning"/ map.put("Father", "Rob"); map.put("Mother", "Kirsten"); System.out.println(map.toString()); } } SECOND CODE WITHOUT WARNING(thanks to you) import java.util.*; public class HelloWorld { public static void main(String[] args) { HashMap map = new HashMap();/"this time no warning"/ map.put("Father", "Rob"); map.put("Mother", "Kirsten"); System.out.println(map.toString()); } }

really ur explaination was good, after watching video i got clear idea about hash map thank you.

Legend

Your videos are very easy to follow !

Hey Love from India ❤️ Your videos are really helpful... Thank you so much.. Plz keep upload more videos 👍

Gosh I wish I could watch ur vid earlier! I just love the way you teach, clear and understandable. PLZ UPLOAD MORE! LUV YA ♥

you're a great teacher, keep going 💪

Thank you for these easy-to-understand tutorials, subscribed now!!

Excellent video, I understood everything. Thank you!

UNDERSTANDABLE !!! Very good video ! Your explanation is clear and simple ! Good job ! I like it.

your voice is so comforting

Helped out at lot! Very concise!

he makes it look and understand so easy.

Alex thanks for making HashMap so easy and simple

Thank you so much!! Finally a good explanation! Can you please make more videos on Data Structures :-)

instead of typing system.out.println() use sout followed by ctrl+space or cmd+space

Bro why does KZfaq keep recommending this. Fine! I’m here. I clicked it

You are the best 🙂 simple and clear without complications 👏👏

your explanations are the best! thank you so much!

You're awesome dude! Very nice and concise explanations!

I must say you are really amazing and good way to explain

This was really helpful. Thank you so much!

So simple explanation. Thanks!

Thank you Alex!! it's always fun and helpful watching your videos :) keep it up!

Thank you ❤

I like your channel! You make it simple

Wow! You made it easy for me! Thank you so much! ❤️❤️

Thanks a bunch for the tutorials man, appreciate it

Thank you for making this. It was extremely helpful!