Introduction to Arrays and ArrayList in Java

In this video we cover Arrays and ArrayList in Java from scratch.

We dive deep into how it works, the memory management, input/output, multidimensional arrays, dynamic arrays, working with functions, and solve some questions.

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👉 Resources

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Timestamps:
0:00 Introduction ‌‍‍‍‌‌‍‍ ‌‍‍‌‌‌‌‍ ‌‍‍‌‍‍‌‍ ‌‍‍‌‍‌‍‌ ‌‍‍‌‍‍‍‌ ‌‌‍‍‌‌‌‌ ‌‌‍‍‍‌‌‌
1:22 Why we need Arrays?
2:58 What is an Array?
3:13 Syntax of an Array
4:26 Direct hit Program : Store 5 Roll Numbers
6:44 How does Array works?
8:42 Internal Working of an Array
10:32 Dynamic Memory Allocation
12:00 Internal Representation of Array
13:06 Continuity of an Array
16:25 Index of an Array
19:53 String Array
20:42 What is null in Java?
23:30 null is used as a default
27:55 Array Input
31:19 for-each loop
33:15 toString() Method
34:52 Array of Objects
36:25 Storage of Objects in Heap
40:21 Array Passing in Function
42:32 Multidimensional Arrays
43:36 Syntax of a 2D Array
45:20 Internal Working of a 2D Array
50:16 2D Array Input
1:01:06 2D Array Output
1:07:05 Dynamic Arrays
1:17:22 Array Functions
1:21:08 Internal Working of ArrayList
1:33:21 Questions
1:33:30 Q1 : Swaping Values in an Array
1:35:20 Q2 : Maximum Value of an Array
1:40:45 Q3 : Reversing an Array
1:44:20 Outro

#arrays #placement #dsa #interviews

[pratikdey]

I searched for a lot of courses on DSA on youtube, used to watch 1 or 2 videos, after that it became boring. But I am addicted to this course and Kunal is slowly becoming an inspiration to me. Thanks Kunal

[nirajpatel]

me: doubt
kunal: don't worry, we will cover it in object oriented programming

[xata]

🎯 Key Takeaways for quick navigation:

01:19 📌 Arrays are collections of data types, and their syntax includes the data type and size declaration.
03:35 📌 Arrays in Java are stored in the heap memory, and heap objects are not guaranteed to be continuous.
09:55 📌 The "new" keyword is used to create objects in Java, including arrays. It's associated with dynamic memory allocation.
16:44 📌 Array indices start from 0, and accessing elements is done using these indices.
20:18 📌 "null" is a special literal in Java representing the absence of a value and is commonly used for uninitialized reference variables.
25:53 📚 2D arrays in Java can be visualized as arrays of arrays, where each individual index holds a reference to an array.
31:23 🔄 You can iterate through array elements using a traditional for loop, an enhanced for-each loop, or utilize the `Arrays.toString()` method for simple printing.
40:07 🔀 Java passes array references to functions by value, allowing functions to modify the original array data.
42:49 🛠️ Defining a 2D array in Java involves specifying the number of rows, while the number of columns can vary for each row.
48:26 🔄 The individual arrays within a 2D array can have varying sizes, making it possible to have jagged arrays where each row has a different number of columns.
51:01 📚 Arrays in 2D can be accessed using index [row][column].
52:40 📚 `array.length` returns number of rows in a 2D array.
56:14 📚 Nested loops are used to input values in a 2D array.
01:00:11 📚 Enhanced for loop simplifies iterating through 2D arrays.
01:04:19 📚 ArrayList in Java allows dynamic resizing without specifying size.
01:15:00 📚 ArrayList in Java is a dynamic data structure similar to arrays but with automatic resizing.
01:17:26 🧬 ArrayList capacity increases dynamically by doubling its size when it reaches a certain threshold.
01:19:39 🔍 ArrayList supports methods like add, remove, update, set, contains, and more for manipulating elements.
01:24:41 ⏰ ArrayList provides an amortized constant-time complexity for adding elements due to its dynamic resizing strategy.
01:35:48 🔄 Swap and find maximum element in an ArrayList can be achieved through simple iterative loops and basic comparison logic.
01:40:48 🔄 Reversing an array using the two-pointer method involves swapping elements from start to end and gradually moving the pointers towards each other.
01:41:28 🔃 The reverse process works for both even and odd-length arrays, utilizing start and end pointers to achieve the reversal.
01:43:05 ✨ The code for reversing an array using the two-pointer approach was demonstrated, showing how to swap and adjust pointers to reverse the array.
01:43:58 🚶‍♂️ The two-pointer method is introduced as a valuable technique, and the session concludes by highlighting the upcoming focus on more advanced array-related questions.
01:44:26 📚 Future sessions will delve into array-related questions, including rotation, palindromic arrays, sliding windows, and two-pointer techniques to enhance problem-solving skills.

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[gauravmp]

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[vedanthbaliga]

Kunal you are the first person who explains the 'internal working' of everything! Every other course I took, the 'why' part was missing and I had lot of questions. Now everything is crystal clear! Keep up the good work! Thanks a lot🙂

[kreynusr]

Kunal, I discovered your channel while I was trying to understand arrays and I have to say you might be one of the best programming tutorial channels out there. You explain everything thoroughly but you do not complicate things. You go in to depth and not only answer the how but the why. Thank you.

[sohandas]

Haven't studied array in my life in such a way that I did today. This course is going to be loved by millions in the upcoming years. Adding a comment so that if someone finds it similar with their thoughts I'll be having notifications. Great job!

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[jhashivam]

See I am not a beginner in java and dsa but still I didn't knew this much knowledge regarding arrays. Indeed it's a very detailed course, kudos to kunal ✌👍🔥

[sachinsharma]

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[jaivishmishra]

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[amruthaa]

I finally learned 2D arrays properly. That's because of you Kunal!! Thank you very much :)

[roshanmhatre]

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The Concepts are cleared so thorough.
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My dear talented brother!

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[_xProfessor]

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[_meghavatichaudhari]

Seriously yaar no one like u ❤️ ur amazing this session I didn't saw any single video on arrays like this . Thanku so much for ur support .

[avanishdubey]

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