Array in Java

Programming in Java

Object Oriented in Java

Advanced topics in Java

Java array is an object which contains similar data type elements. In Java array a fixed no of elements can be stored.
Array in java is index-based, the index of first element in array is 0 while the last index is [size-1] .

Array may be single dimensional or multidimensional.

Single dimensional array :

It may be declared as following:
int a[]=new int[10];
Here name of the array is a and size of the array is 10.
So, index of the array elements will be 0-9.

How the array elements are accessed.

a[2]=55;
the above statement stores 5 value at 2 index of the array.
Declaration with initialization may be as following :
String name[]={“rahul“,”sunil“,”jyoti“};

Program to take 10 numbers from user as command line argument in an array and print the elements in reverse order.

class ArrayExample
{
  public static void main(String args[])
  {
    // declare an array of 10 size.
    int a[]= new int[10];
    for(int i=0;i<10;i++)
      {
         //take input as command line arguments and convert it into integer.
         a[i]=Integer.parseInt(args[i]);
       }
    // print the array elements in reverse order.
    for(int i=9; i>=0; i--)
      {
         System.out.println("array elements: "+a[i]);
      }
   }
}

Multi Dimensional (2D) Array:

int a[][]= new int[3][2];
where 3 is the no of row and 2 is no of column.
Eg: a[0][0] is the element at 0 row and 0 column.

In Java different number of columns may be created for each row ,

int a[][]= new int[3][]; // the [no. of columns] field is left empty here and is assigned below.
a[0]= new int[1];
a[1]= new int[2];
a[2]= new int[3];
In this case, every rows has different no. of columns or we can say zig zag array may be created.