Arrays in Java Programming

Arrays in Java Programming

Arrays in Java Programming are objects that store elements of the same data type. The elements of an array are stored in a contiguous memory location.

• • Only a fixed number of elements can be stored in an array.
  • In Java, the array is index-based; the first element is indexed at index 0, the second element is indexed at 1, and so on such that the last element is stored at index n-1 where n is the number of elements of the array.
  • The length of the array in Java can be obtained by using length members.
  • Java arrays can store both primitive and object data types.
  • Java array inherits the Object class and implements Serializable as well as Cloneable interfaces.

 

 

Array Creation in Java Programming

In Java, the syntax of array creation is as follow:

Syntax:

int[] arr=new arr[10];

The array created above is of type int and can store 10 elements at a contiguous memory location. 

 

 

Array Initialization in Java Programming

Arrays in Java Programming can be initialized in two ways:

• Initializing elements individually on separate lines

• Initializing elements in a single line

 

Initializing elements individually on separate lines

After array creation, elements are assigned a value of a valid data type individually using indexing. Syntax of such initialization is given below:

Syntax:

int[] arr=new arr[5];
arr[0]=1;
arr[1]=2;
arr[2]=3;
arr[3]=4;
arr[4]=5;

Initializing elements in a single line

After array creation, the array is initialized by separating elements by a comma and then enclosed with a set of curly braces {}. Syntax of such initialization is given below:

Syntax:

int[] arr={1,2,3,4,5};

 

 

Access Elements of an Array in Java Programming

In Java, elements of an array are accessed using its index number.

Example to access Array Elements in Java:

//Java Program to access elements of an array
public class ArrayAccess {
    public static void main(String[] args) {
        //Array declaration and initialization
        int[] arr={1,2,3,4,5};

        //Accessing element at index 4 using the index
        System.out.println("Element at index 4 is: "+arr[4]);
    }
}

Output:

Element at index 4 is: 5

 

 

Modify Elements of an Array in Java Programming

Elements of an array can be modified using its index number and assigning it a new value after accessing it.

Example to modify Array Elements in Java:

//Java program to modify elements of an array
public class ArrayModify {
    public static void main(String[] args) {
        //Array declaration and initialization
        int[] arr={1,2,3,4,5};

        //Accessing element at index 4 using the index
        System.out.println("Element at index 4 before modification is: "+arr[4]);

        //Accessing element at index 4 using the index and assigning it a new value
        arr[4]=10;
        System.out.println("Element at index 4 after modification is: "+arr[4]);
    }
}

Output:

Element at index 4 before modification is: 5
Element at index 4 after modification is: 10

 

 

Number of Elements in an Array in Java Programming

A number of elements in an array can be obtained using the length member or property of the Array class.

Example to find number of Array Elements in Java:

//Java program to find number of elements in an array
public class ArrayLength {
    public static void main(String[] args) {
        //Array declaration and initialization
        int[] arr={1,2,3,4,5};

        //Length of the array
        System.out.println("Number of elemnets in arr[] is: "+arr.length);
    }
}

Output:

Number of elemnets in arr[] is: 5

 

 

For Loop over an Array in Java Programming

Loop are used with arrays to efficiently access their elements and do necessary manipulations.

//Java Program to display array elements using for loop
public class ArrayForLoop {
    public static void main(String[] args) {

        //Array declaration and initialization
        int[] arr={1,2,3,4,5};

        //Displaying array elements using for loop
        for(int i=0;i<arr.length;i++){
            System.out.println("arr["+i+"] is "+arr[i]);
        }
    }
}

Output:

arr[0] is 1
arr[1] is 2
arr[2] is 3
arr[3] is 4
arr[4] is 5

 

 

For-each Loop over an Array in Java Programming

For-each loop is generally used to traverse the array and is element-based.

//Java Program to traverse an array using for-each loop
public class ArrayForEach {
    public static void main(String[] args) {
        //Array declaration and initialization
        String[] sentence={"Welcome","to","StudyExperts","!"};

        for(String word:sentence){
            System.out.print(word+" ");
        }
    }
}

Output:

Welcome to StudyExperts !

 

 

Multi-dimensional Array in Java Programming

The multi-dimensional array can be considered an array of arrays. An array of any dimensions can be created in Java and loops are used to work with them.

Syntax of Multi-dimensional Array Declaration:

//2-dimensional array
int[][] arr1;

//3-dimensional array
int[][][] arr2;

Syntax of Multi-dimensional Array Declaration and Initialization:

//2-dimensional array with 2 rows and 3 columns for each row
int[][] arr={{1,2,3},{4,5,6}};

Example of multi-dimensional array in Java:

//Java Program with 2-dimensional array
public class ArrayTwoD {
    public static void main(String[] args) {

        //Array declaration and Initialization
        int[][] arr={{1,2,3},{4,5,6},{7,8,9}};
        
        //Nested For Loop
        for(int i=0;i<arr.length;i++){
            for(int j=0;j<arr[i].length;j++){
                System.out.print(arr[i][j]+" ");
            }
            System.out.println();
        }
    }
}

Output:

1 2 3 
4 5 6 
7 8 9