If you’re new to programming but want a career in tech, I HIGHLY RECOMMEND applying to one of Springboard’s online coding bootcamps (use code ALEXLEE for $1,000 off): bit.ly/3HX970h
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
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.
It’s not complicated to use but the implementation of a hash map is a bit more complex than just a 2d array. Hashmaps use a hash function to store the key value pair so that it doesn’t have to go through the whole hashmap using a for loop, Big O(n), when looking for a key. The hash function lookup makes it so that it is Big O(1). In other words the hash function makes it so that the lookup of a key is faster.
I don't know if you'll see this since it's an older video but you're probably the only programming tutorial RUclipsr 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.
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.
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.
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.
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.
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!
If you are 2 years into a computer science degree and you do not understand the basics of search time algorithms or hashing then either cut your losses and leave or find another service provider
This was extremely helpful in helping me understand hashmaps. I wasn't understanding them in lectures but this definitely helped clear things up. Thanks!!!
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!
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!
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()); } }
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
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
Thank you so much. This helps me assign 1000 "dollars" to each new player. I am making a balance/economy plugin for a minecraft server and this also helps a lot with transactions
i am an indian and i actually dont watch englishmen video because i couldnt get the pace of english, but you are the 1st youtuber whose video i watch very confidently. my request is that can you start a series to make people competetive coder from 0 to hero.
If you’re new to programming but want a career in tech, I HIGHLY RECOMMEND applying to one of Springboard’s online coding bootcamps (use code ALEXLEE for $1,000 off): bit.ly/3HX970h
This is actually the best description of HashMaps I have seen yet
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
:D
Thank you for this!
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.
It’s not complicated to use but the implementation of a hash map is a bit more complex than just a 2d array. Hashmaps use a hash function to store the key value pair so that it doesn’t have to go through the whole hashmap using a for loop, Big O(n), when looking for a key. The hash function lookup makes it so that it is Big O(1). In other words the hash function makes it so that the lookup of a key is faster.
I don't know if you'll see this since it's an older video but you're probably the only programming tutorial RUclipsr 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.
He understands what not knowing something was like. I really appreciate that!
This video is awesome. Your english is clear and understandable. I like it 👍
Here, after concentrating to get what was said in the Indian accent, one time too often.
@@7own878 it gets tiring to heat the same accent from computer science tutorials all the time
I know...we can actually understand this man, unlike all the other idiots who make tutorials
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!
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!
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
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.
For anyone with a python background, hashmaps are the same as dictionaries.
Thank you bigman
Yes
Thank you
Ah the more you know.
Saved me 11 minutes !
This is so helpful. Your explanations and presentation are perfect.
just as simple as u.thanks.it is a one kind of social work.we need people like u.
Thank you very much Alex! I was struggling with HashMap for all day, and your video really helped!!
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..
the most simplified yet extremely informative tut on hashmap. great work m8 :)
I finally understood, thanks for the video!! Btw the sound of your keyboard is so satisfying😨
now that's amazing how something so abstract to me has become instantly crystal clear. you are awesome!
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!
If you are 2 years into a computer science degree and you do not understand the basics of search time algorithms or hashing then either cut your losses and leave or find another service provider
@@richardpaynton8766 I appreciate the advice, but I only have 1 term left now until I graduate. But yes, my teacher was terrible.
Thank you for explaining things so well. You make otherwise complicated things sound so easy to understand. Bless you brother!
Couldnt imagine a better tutorial out there!
Great Video man!
Been studying for my Software Engineering Interview, and these videos are so helpful!
This young dude is my favorite tutor in youtube !!
for anyone that is wondering, it is called a HashMap because it uses a technique called hashing.
Most useful on teaching me hashmaps, Thank you so much!
That keyboard is amazing! Thanks for clearing up hashmaps for me, makes it easier when we get there at school.
thank you for making coding tutorials that arent mind numbing
Your Videos are straight to the point , My Coding phobia isn't anymore because of your videos...
i don't usually write comments but your tutorials are so good and helpful.
keep going !
The UI you created it beautiful!
You make everything so simple. Thanks a lot !
you don't give weird analogies like other youtube videos good work
lovely dialogue delivering, excellent quality of video, concepts told in lay man terms. enjoyed and learnt. keep up the good work Alex. :)
This was extremely helpful in helping me understand hashmaps. I wasn't understanding them in lectures but this definitely helped clear things up. Thanks!!!
love the teachers who make understanding fun. thank you sir
I definitely recommend Alex's video! Easy to understand and follow!
You are great my son. May God Bless you.I am 48 but steel I am your student. Thank you very much.
Thank you for the video. This covers almost everything for novice learners.
These tutorials are awesome. You make java look so easy. Thanks for these easy tutorials!!
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!
Your videos are amazing! Thank you!!! You break down complex things so that I can better understand what's actually going on
I finally understand HashMaps. Thank you so much!
As usual GREAT! Understanding the concept in 11 minutes :)
Legend
Damn, his Java tutorials are totally understandable, thanks
Thanks for taking time to create content that helps me understand Java! Great job!
Wow thank you I was unable to understand hash maps until I stumbled upon your video. Thank you :)
that's just straight as an arrow. Awesome bro.
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. :)
You sound gay do you want to get on your knees for him
Extremly good explained!
Way better then my proffesor! Sure its not advanced, but i at least undertood the basicis of HashMap.
Thank you.
Teaching method really awesome. Wish your good health.
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!
great tutorial. I understand it alot than my teacher. Thanyou! post more java tutorial
My favorite java tutor. if I am not mistaking if u want order you can use TreeMap
You're the best coding tutor!
UNDERSTANDABLE !!! Very good video ! Your explanation is clear and simple ! Good job ! I like it.
Thank you for these easy-to-understand tutorials, subscribed now!!
Gosh I wish I could watch ur vid earlier! I just love the way you teach, clear and understandable. PLZ UPLOAD MORE! LUV YA ♥
Hey
Love from India ❤️
Your videos are really helpful...
Thank you so much..
Plz keep upload more videos 👍
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());
}
}
Best hashmap tutorial ever!
you're a great teacher, keep going 💪
You do a great job! Simple and clear! Thank you.
really ur explaination was good, after watching video i got clear idea about hash map thank you.
pls make a full session on java , your style is best .
Damn. It was sooo clear. Relly liked it! Thumb up and subscribed :)
Thank you Alex!! it's always fun and helpful watching your videos :) keep it up!
Thank you ❤
You're awesome dude! Very nice and concise explanations!
You simplified it perfectly.. thank you sir
Its called HashMap because it's a data structure that uses the hash function to generate a mapping of keys and their corresponding values.
Hey Alex you're amazing I really love the way you teach...Stay happy 😉
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
Your videos are very easy to follow !
Excellent video, I understood everything. Thank you!
Thank you so much, you're an awesome teacher.
Really good tutorial dude. Finally someone who dont have a crappy mic and a indian accent :D
pd : the editing was amazing too!
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
your voice is so comforting
You are the best 🙂 simple and clear without complications 👏👏
Bro why does RUclips keep recommending this. Fine! I’m here. I clicked it
you explained it effortless
Wow!
You made it easy for me!
Thank you so much! ❤️❤️
Thank you so much. This helps me assign 1000 "dollars" to each new player. I am making a balance/economy plugin for a minecraft server and this also helps a lot with transactions
Helped out at lot! Very concise!
i am an indian and i actually dont watch englishmen video because i couldnt get the pace of english, but you are the 1st youtuber whose video i watch very confidently. my request is that can you start a series to make people competetive coder from 0 to hero.
Very nice man! Helped me a lot👍🏼
Thank you for making this. It was extremely helpful!
Your videos are very useful sir. Thank You so much for your good explanation
Amazing Video!!!!!!! keep going!!! can't wait to learn more.
I must say you are really amazing and good way to explain
This was really helpful. Thank you so much!
This Channel is underrated
Wow ...such an amazing explanation
Thank Alex, very clear explanation of HashMap.