Arrays are used to store similar types of elements in sequential manner. Arrays are fixed in size. You can not grow or shrink the size of array once initialized. Example –
 
int [] a = {11,22,33}

Student [] studentArray = {s1,s2,s3}
There are 3 types of arrays in Java.
  • Single Dimensional
  • 2-Dimensional
  • Multi-dimensional

Single dimensional Array

Two dimensional Array

Below example explains how to use arrays in Java.
 
package arrays;

/**
 * Created by ssalunke on 18/04/2016.
 */
public class Array {

    public static void main(String [] args){

        System.out.println("Let us learn One dimensional array");

        int[] primitiveIntArray = new int[3];
        int[] primitiveInitializedIntArray = {1,2,3};
        int[] primitiveInitializedIntArray1 = new int[]{1,2,3};

        //Just like primitives, we can store the reference 
        // types of objects in Arrays
        Student s1 = new Student("s1");
        Student s2 = new Student("s2");
        Student s3 = new Student("s3");

        Student[] studentArray = new Student[3];
        Student[] studentInitializedIntArray = {s1,s2,s3};
        Student[] studentInitializedIntArray1 = new Student[]{s1,s2,s3};

        //Accessing elements in array by using for loop
        for(int i=0;i<=2;i++){
            System.out.println("Integer Array -> "
                    + primitiveInitializedIntArray[i]);
            System.out.println("Student Array -> "
                    + studentInitializedIntArray[i]);
        }

        //Accessing elements in array using another variation of for loop
        for(int e: primitiveInitializedIntArray){
            System.out.println("Integer Array -> " + e );
        }
        for(Student e: studentInitializedIntArray){
            System.out.println("Student Array -> " + e );
        }

        //***************************************************************//
        //Learning 2 dimensional arrays
        int [][] twoDimensionalIntArray = new int[3][3];
        for(int i=0;i<=2;i++)
            for(int j=0;j<=2;j++)
            {
                twoDimensionalIntArray[i][j] = i+j;
            }

        for(int[] e: twoDimensionalIntArray){
            for(int j:e)
                System.out.println("2-D Integer Array -> " + j);
        }

        //Array of Arrays in Java
        int[][] intArrayOfArray = 
                {primitiveInitializedIntArray,primitiveInitializedIntArray1};
        int[][][] intArrayOf2DArray =
                {twoDimensionalIntArray,twoDimensionalIntArray};

        System.out.println("1st Element in intArrayOfArray -> " 
                + intArrayOfArray[0][0]);
        System.out.println("1st Element in intArrayOf2DArray -> " 
                + intArrayOf2DArray[0][0][0]);

    }

}

class Student{
    String name;

    Student(String s){
        this.name = s;
    }

    @Override
    public String toString(){
        return this.name;
    }
}
Here is the output of above example.

Let us learn One dimensional array
Integer Array -> 1
Student Array -> s1
Integer Array -> 2
Student Array -> s2
Integer Array -> 3
Student Array -> s3
Integer Array -> 1
Integer Array -> 2
Integer Array -> 3
Student Array -> s1
Student Array -> s2
Student Array -> s3
2-D Integer Array -> 0
2-D Integer Array -> 1
2-D Integer Array -> 2
2-D Integer Array -> 1
2-D Integer Array -> 2
2-D Integer Array -> 3
2-D Integer Array -> 2
2-D Integer Array -> 3
2-D Integer Array -> 4
1st Element in intArrayOfArray -> 1
1st Element in intArrayOf2DArray -> 0
Complex problems, Simple Solutions