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Pavithra C
Pavithra C

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Day-40:Array in java

Array
An array is a container object that holds a fixed number of values of a single type. The length of an array is established when the array is created. After creation, its length is fixed.

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The following program, ArrayDemo, creates an array of integers, puts some values in the array, and prints each value to standard output.

class ArrayDemo {
    public static void main(String[] args) {
        // declares an array of integers
        int[] anArray;

        // allocates memory for 10 integers
        anArray = new int[10];

        // initialize first element
        anArray[0] = 100;
        // initialize second element
        anArray[1] = 200;
        // and so forth
        anArray[2] = 300;
        anArray[3] = 400;
        anArray[4] = 500;
        anArray[5] = 600;
        anArray[6] = 700;
        anArray[7] = 800;
        anArray[8] = 900;
        anArray[9] = 1000;

        System.out.println("Element at index 0: "
                           + anArray[0]);
        System.out.println("Element at index 1: "
                           + anArray[1]);
        System.out.println("Element at index 2: "
                           + anArray[2]);
        System.out.println("Element at index 3: "
                           + anArray[3]);
        System.out.println("Element at index 4: "
                           + anArray[4]);
        System.out.println("Element at index 5: "
                           + anArray[5]);
        System.out.println("Element at index 6: "
                           + anArray[6]);
        System.out.println("Element at index 7: "
                           + anArray[7]);
        System.out.println("Element at index 8: "
                           + anArray[8]);
        System.out.println("Element at index 9: "
                           + anArray[9]);
    }
}
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output:

The output from this program is:

Element at index 0: 100
Element at index 1: 200
Element at index 2: 300
Element at index 3: 400
Element at index 4: 500
Element at index 5: 600
Element at index 6: 700
Element at index 7: 800
Element at index 8: 900
Element at index 9: 1000
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Declaring a Variable to Refer to an Array

The preceding program declares an array (named anArray) with the following line of code:

// declares an array of integers
int[] anArray;

Like declarations for variables of other types, an array declaration has two components: the array's type and the array's name. An array's type is written as type[], where type is the data type of the contained elements; the brackets are special symbols indicating that this variable holds an array. The size of the array is not part of its type (which is why the brackets are empty).[TBD]

Similarly, you can declare arrays of other types:

byte[] anArrayOfBytes;
short[] anArrayOfShorts;
long[] anArrayOfLongs;
float[] anArrayOfFloats;
double[] anArrayOfDoubles;
boolean[] anArrayOfBooleans;
char[] anArrayOfChars;
String[] anArrayOfStrings;

public class Main {
    public static void main(String[] args)
    {

        // initializing array
        int[] arr = { 1, 2, 3, 4, 5 };

        // size of array
        int n = arr.length;

        // traversing array
        for (int i = 0; i < n; i++)
            System.out.print(arr[i] + " ");
    }
}
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  1. Create an Array To create an array, you need to allocate memory for it using the new keyword: 
// Creating an array of 5 integers
int[] numbers = new int[5];
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  1. Access an Element of an Array[TBD] We can access array elements using their index, which starts from 0: 
// Setting the first element of the array
numbers[0] = 10; 

// Accessing the first element
int firstElement = numbers[0];
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  1. Change an Array Element To change an element, assign a new value to a specific index: 
    // Changing the first element to 20
    numbers[0] = 20;
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  1. Array Length We can get the length of an array using the length property: 
    // Getting the length of the array
    int length = numbers.length;
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Creating, Initializing, and Accessing an Arrays in Java

For understanding the array we need to understand how it actually works. To understand this follow the flow mentioned below:

  1. Declare
  2. Initialize
  3. Access

1. Declaring an Array
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Reference link:
https://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html

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