Arrays in java

This section contains the detail about the Arrays in java.

Arrays in Java

An array is the set of similar type of elements which is stored under a common name. An array can acquire any type and can have one or more dimensions. The element in array can be accessed by it's index. For storing related information under the same roof , we use arrays.

Declaring one dimension array 

type var-name[ ];

For example :

int[] Dev ;

or , you can also declare it as follows :

int Dev[];

If an array is declared as : int Dev[3], it means it has 4 element from Dev[0] to Dev[3].

Allocating memory to arrays :

var-name = new type[size];  

Example :

Dev = new int[12];

Assigning and accessing value from array

You can assign value directly, like this :

Dev[0] = 12; // this will assign value to first element.
Dev[1] = 30  // this will assign value to second element.

Array can also be assigned when they are declared as :

int Dev[] = {3, 12, 21, 30, 39, 48};

You can access array element like this :

System.out.println(Dev[3]);   // This will print 4th element of array.

Example :

public class DevArray {
public static void main(String[] args) {
double[] devList = {1.9, 2.9, 3.4, 3.5};

// Print all the array elements
for (double element: devList) {
System.out.println(element);
}
}
}

Output :

C:\Program Files\Java\jdk1.6.0_18\bin>javac DevArray .java C:\Program Files\Java\jdk1.6.0_18\bin>java DevArray 1.9 2.9 3.4 3.5

Multidimensional array :

In java, multidimensional arrays are actually arrays of arrays. For example, you can declare a two dimensional array as :

int twoD[][]=new int [4][5];

You can also declare a three dimensional array as :

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

Example :

Class TwoDmatrix{
  public static void main(String args[]) {
    int twoDm[][]= new int[4][5];
    int i,j,k=0;

    for(i=0;i<4;i++)
      for(j=0;j<5;j++) {
         twoDm[i][j]=k;
         k++;
      }
    for(i=0;i<4;i++)
      for(j=0;j<5;j++) {
         System.out.println(twoDm[i][j]+"")
         System.out.println();
      }
   }
 }
 

Output :

C:\Program Files\Java\jdk1.6.0_18\bin>javac TwoDmatrix .java C:\Program Files\Java\jdk1.6.0_18\bin>java TwoDmatrix 0  1  2  3  4 5  6  7  8  9 10 11 12 13 14 15 16 17 18 19

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