Types of Array in Java and It's Declaration

Declaration of array

A Java array variable is declared just like, you would declare a variable of the desired type, except you add [] after the type. Here is a simple Java array declaration example:

int[]Array;

So, it follows the structure:

dataType[]ArrayName;

These are some more examples:

double[] List;

String[] Names;

int[] Record;

When you declare a Java array variable you only declare the variable (reference) to the array itself. The declaration does not actually create an array. To create an array, following the declaration, the following format is used:

dataType[]ArrayName;

ArrayName = new dataType[size];

The following syntax can also be applied to declare and create and array:

dataType[]ArrayName = new dataType[size];

For example,

String[] Names = new String[7];

int[] Marks = new int[9];

This method is simpler and more concise.

After this, the array can be initialized by storing the elements:

The syntax is for this is,

dataType[] ArrayName = {element1, element2...};

For example

double[] List = {1.9, 2.9, 3.4, 3.5};

Or it can be done in this way:

dataType[] ArrayName = new dataType[size];

ArrayName[0]=element1;

...

ArrayName[size-1]=elementsize;

For example,

int a[]=new int[5];

a[0]=10;

a[1]=20;

a[2]=70;

a[3]=40;

a[4]=50;

The position in this case can be given in three ways:

1. Integer constant

E.g.

a[2]=4;

2. Integer variable

E.g.

int x=5;

a[x]=3;

3. Arithmetic operation

E.g.

int x=5;

a[x+1]=3;

Types of arrays

There are two types of arrays in Java based on dimensions:

1. Single-Dimensional Array
2. Multi-Dimensional Array 

Single-Dimensional Array

A Single-Dimensional Array is a structured collection of components (often called array elements) that can be accessed individually by specifying the position of a elements with a single index value. They have only one subscript value and store data in a linear form.

An example of a Single-Dimensional Arrays is a list.

The syntax for such an array is the same as has been described in the Declaration of an array section. It is as follows:

The first method is:

Declaration-> dataType[] ArrayName = {e1, e2........};

Example

int[] scores = {5, 10, 20, 50};

The other method is:

dataType[]ArrayName; -> Declaration

ArrayName = new dataType[size]; -> Creation of array

ArrayName[0]=element1;

.................

.................

ArrayName[size-1]=elementsize;

Example:

String[] Employees;

Employees = new String[2];

Employees[0]=”Rahul”;

Employees[1]=”Manish”;

1D- Array Example:

class example1d
{
  public static void main(String args[])
  {
    int m[] = new int[5];
    m[0] = 50;
    m[1] = 60;
    m[2] = 70;
    m[3] = 80;
    m[4] = 90;
    System.out.println("The marks for 5 students are:");
    for(int i = 0; i < 5; i++)
    {
    System.out.print(+m[i]);
        System.out.println();
    }
  }
} 

Multi-dimensional arrays

An array that has more than 1 subscript is known as a multi-dimensional array. A one-dimensional array stores data in a linear form however a multi-dimensional array can store more information. So it can be thought of as an array of one-dimensional arrays.

Note: The most common example of a one-dimensional array is a list, the primary example of a multi-dimensional array is a table.

The syntax for multi-dimensional arrays is:

dataType [ ][ ] ArrayName = new dataType[][];

This will create a two-dimensional array.

Note: With each “[]” added, the number of dimensions increases by one.

For example,

int [ ][ ][ ] 3d = new int[4][3][5];

This creates a three-dimensional array of integer values.

Method to Define 2D Array:

int [ ][ ] 2d = new int[2][3];

2d[0][0] = 30;

2d [0][1] = 40;

2d [0][2] = 50;

2d [1][0] = 10;

2d [1][1] = 20;

2d [1][2] = 30;

The output is:

30 40 50

10 20 30

Another way to represent 2D Array:

int[][] 2d = { { 30, 40, 50 },

{ 10, 20, 30 }

};

The output is the same as above.

Example program for multi-dimensional array:

class multidexample
{
   public static void main(String[] args)
   {
        int[][] a = {{2,3,4},{1,3,5},{9,7,5}
            };
        int[][] b = {{70,80,90},{56,38,59},{19,27,15}
               };      
    int[][] c = new int[3][3];  
    for (int i = 0; i < 3; i++)
    {
           for (int j = 0; j < 3; j++)
        {
               c[i][j] = a[i][j] + b[i][j];
               }
        }
       System.out.println("Sum of the two matrices is");
       for (int i = 0; i < 3; i++)
    {
           for (int j = 0; j < 3; j++)
        {
               System.out.print(c[i][j] + " ");
               }
           System.out.println();
        }
   }
}

 

Join an ISO Certified core java training institute for online and classroom training. 

Course Duration: 45 Days