# 1D Arrays_1

## What are arrays?
> Array is a collection of same DataType values/variables.

> By default a new integer array is created with all elements as 0.

## How to create an array?
1. datatype name[] = new datatype[size]

Code1 :

    int ar[] = new int[5]  

Explanation :

    Integer array of size 5 in name of ar created

2. datatype []name = new datatype[size]

Code2 :

    int []ar = new int[5] 

Explanation :

    integer array of size 5 in name of ar created

3. datatype[] name = new datatype[size]

Code3 :

    int[] ar = new int[5] 

Explanation :

    integer array of size 5 in name of ar created

4. We can directly create an array by giving values

Code4 :

    int ar[] = {33,3,4,5,6,7};

Explanation :

    A new array of size 6 is created with elements: {33,3,4,5,6,7}

Note: We can create array using any of the above methods.

## Indexing in an array

> Indexing in an array starts from 0 and goes till N - 1 (N being length of array). It means index of first element is 0 and index of last element is N - 1.

1. We access these indexes by following syntax: array_name[index number]

Code1 :

    int ar[] = new int[5];
    System.out.println(ar[0]);

Output:

    0

Explanation :

    By default all elements in a new array are 0.

2. Index out of Bound :

Code2 :

    int ar[] = new int[5];
    System.out.println(ar[6]);

Output :

    Error: ArrayIndexOutOfBoundsException

Explanation :

    In above array it does not have index 6.

3. Finding length of an array (array_name.length):

Code3 :

    int ar[] = new int[5];
    System.out.println(ar.length);

Output :

    5

Explanation :

    We have total 5 elements in this array.

4. We can store values using indexes:

Code4 :

    int ar[] = new int[4];
    ar[0] = 12;
    ar[1] = 34;
    ar[2] = 2;
    ar[3] = 21;

Output :

    Final array: {12, 34, 2, 21} having size 4.

## Iterating over an array to access/print values:
1. Lets say we have an array of size 3: ar[3] = {4, 3, 5}. Then we can acces these values using index:

Code :

    System.out.print(arr[i])  

Output :

    It will print value at ith index

2. We are printing values of an array one by one using indices.
Code :

    System.out.print(arr[0]) // It will print -> 4
    System.out.print(arr[1]) // It will print -> 3
    System.out.print(arr[2]) // It will print -> 5

3. Let us write a function that prints all the elements of a given array.
Code :

    static void printArray(int[] a){
        for(int i = 0; i < a.length; i++){
            System.out.println(a[i]);
        }
    }
    public static void main(String args[]){
        int[] arr = {33, 3, 4, 5};
        printArray(arr);

    }

Output :

    33
    3
    4
    5

Explanation :

    In above code we are passing our array to a function to iterate in the given array.

4. We can create array by taking values as input from user.

Code :

    Scanner sc = new Scanner(System.in);

    int ar[] = new int[5];
    for (int i = 0; i < 5; i++) {
        ar[i] = sc.nextInt();
    }

Input:

    1
    2
    3
    4
    5

Explanation :

    ar = {1, 2, 3, 4, 5} is created.

## Creating a new array using an old array name :

Code :

int ar[] = new int[3];
ar[0] = 10;
ar[1] = 20;
ar[2] = 30;
ar = new int[4];
System.out.print(ar[0]);

Output :

0

Explanation :

If we use existing array's name to create new array then that name will be allocated to new array only.