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README.md		README.md
cwh_26_arrays.java		cwh_26_arrays.java

README.md

Java Tutorial: Introduction to Arrays

An array is a collection of similar types of data having contiguous memory allocation.
The indexing of the array starts from 0., i.e 1st element will be stored at the 0th index, 2nd element at 1st index, 3rd at 2nd index, and so on.
The size of the array can not be increased at run time therefore we can store only a fixed size of elements in array.
Use Case: Storing marks of 5 students

Accessing Array Elements :

Array elements can be accessed as follows,

/* marks[0] = 100       //Note that index starts from 0
marks[1] = 70
.                                  
.
marks[4] = 98 */

So in a nut shell, this is how array works:

int[] marks; //Declaration!
marks = new int[5];   //Memory allocation!

int[] marks = new int[5]; //Declaration + Memory allocation!

int[] marks = {100,70,80,71,98} // Declare + Initialize!

Note : Array indices start from 0 and go till (n-1) where n is the size of the array.

Array length :

Unlike C/C++, we don't need to use the sizeof() operator to get the length of arrays in Java because arrays are objects in Java therefore we can use the length property.
```
marks.length //Gives 5 if marks is a reference to an array with 5 elements
```

Displaying an Array :

An array can be displayed using a for loop:

for (int i=0; i<marks.length; i++)
{
            Sout(marks[i]);    //Array Traversal
}

Quick Quiz: Write a Java program to print the elements of an array in reverse order.

public class cwh_26_arrays {
    public static void main(String[] args) {
    int [] marks = {98, 45, 79, 99, 80};
    for (int i=marks.length-1; i>=0; i--) {
        System.out.println(marks[i]);
        }
    }
}

Code as Described in the Video

package com.company;

public class cwh_26_arrays {
    public static void main(String[] args) {
        /* Classroom of 500 students - You have to store marks of these 500 students
        You have 2 options:
        1. Create 500 variables
        2. Use Arrays (recommended)
        */
        // There are three main ways to create an array in Java
        // 1. Declaration and memory allocation
        // int [] marks = new int[5];

        // 2. Declaration and then memory allocation
        // int [] marks;
        // marks = new int[5];
        // Initialization
        // marks[0] = 100;
        // marks[1] = 60;
        // marks[2] = 70;
        // marks[3] = 90;
        // marks[4] = 86;

        // 3. Declaration, memory allocation and initialization together
        int [] marks = {98, 45, 79, 99, 80};

        // marks[5] = 96; - throws an error
        System.out.println(marks[4]);
    }
}

Handwritten Notes: Click to Download

Ultimate Java Cheatsheet: Click To Download

Java-Tutorials/26.Introduction_To_Arrays at main · kishanrajput23/Java-Tutorials · GitHub

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