Armstrong number in java with Examples

Armstrong number is nothing but the sum of its digits each raised to the power of the number of digits. Before Michael F. Armstrong named it Armstrong number, it was known as Narcissistic number. 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 153, 370, 371, 407, 1634, 8208, 9474,… this is a series of the Armstrong numbers. Now let’s find out whether a given number is an Armstrong number or not in this Armstrong Number in java article.

How to identify an Armstrong number

If the sum of the digits each of them raised to the power of the number of digits is equal to the original number then it is called an Armstrong number. Let’s understand the logic behind this with an example given below.

Logic in Armstrong number

Suppose,
PQSR is a integer then,
PQRS = Pn+ Qn+Rn+Sn    
Where n is the digits count.
If PQRS is equal to the Pn+ Qn+Rn+Sn then, it is an Armstrong number.

Example 1

Input number = 146
1³ + 4³ + 6³ = 1*1*1 + 4*4*4 + 6*6*6 = 281
Hence, it is not an armstrong number

Example 2

Input number = 1634
14 + 64 + 34 + 44 = 1*1*1 + 6*6*6 + 3*3*3 + 4*4*4  = 1634
Hence, it is an Armstrong number 

Armstrong number program in java

Here we have given four programs for finding Armstrong number like using for loop, recursive function, while loop, and in between the range. 

Armstrong number in java using while loop

Example

import java.util.Scanner;

public class armstrong_number {

    
    public static void main(String[] args) {
        
        int number =0;
        int result = 0, rem; //variables for calculation
        int x;
        
        Scanner object = new Scanner(System.in); //using scanner class for accepting input from user
        System.out.println("Input a positive integer");
        number = object.nextInt();
        
        x = number;
        while (x!= 0) // loop with exit condition n is not equal to 0
        {
            rem = x% 10;
            result = result + rem*rem*rem;  // logic for finding armstrong number
            x = x/10;
        }
           
        if(number == result) //check if original number and addition is same or not
            System.out.print("This is an Armstrong number\n");
        else
            System.out.print("This is not an Armstrong number\n");
    }        
}

Output

Enter a number:370
This is an Armstrong number

Enter a number:20
This is an Armstrong number

Armstrong number in java using recursive function

Example

import java.util.Scanner;

public class armstrong_number {

    int find(int num, int total) //static function for identifying armstrong number
    {
        int n;
	while(num!=0)
	{
		n=num%10;
		total=total+(n*n*n); //logic for armstrong number
		num/=10 ; 
	}
	return total;
    }
    
    public static void main(String[] args) {
        
        int n1, n2;
        int result = 0;
        
        Scanner sc = new Scanner(System.in); // using scanner class for accepting number from user
        System.out.print("Enter starting of range:");  
        n1 = sc.nextInt();
        System.out.print("Enter ending of range:");
         n2 = sc.nextInt();
         
         armstrong_number arm = new armstrong_number();
         
         for(int i=n1;i<n2;i++) // loop for travalling from starting point to ending point
	{
	result = arm.find(i,0);
	if(result == i)
	      System.out.println(i);
	}
    }
}

Output

Enter starting of range:100
Enter ending of range:1000
153
370
371
407

Print Armstrong number in between n to m range 

Example

import java.util.Scanner;

public class armstrong_number {

    static int arm(int num) //static function for identifying armstrong number
    {
        int n,total=0;
	while(num!=0)
	{
		n=num%10;
		total=total+(n*n*n); //logic for armstrong number
		num/=10 ; 
	}
	return total;
    }
    
    public static void main(String[] args) {
        
        int n1, n2;
        int result = 0;
        
        Scanner sc = new Scanner(System.in); // using scanner class for accepting number from user
        System.out.print("Enter starting of range:");  
        n1 = sc.nextInt();
        System.out.print("Enter ending of range:");
         n2 = sc.nextInt();
         
         while(n1<n2)  // loop for finding armstrong numbers in igiven range
         {
             result = arm(n1); //call to static function
             if(result == n1)
                 System.out.println(n1); //prints the armstrong number 
             n1++;
         }
    }
}

Output

Enter starting of range:100
Enter ending of range:1000
153
370
371
407

Armstrong number in java using for loop

Example

import java.util.Scanner;

public class armstrong_number {

    public static void main(String[] args) {
        int num=0;
        int n, remainder, result = 0, i = 0;
        
        
        Scanner sc = new Scanner(System.in); // using scanner class for accepting number from user
        System.out.print("Enter a number : ");  
        num = sc.nextInt();
        
        n = num;
        
        for (;n != 0; n /= 10)
        {
            i++;
        }
        n = num;
        for (;n != 0; n /= 10)
        {
            remainder = n % 10; //logic for armstrong number
            result += Math.pow(remainder, i);  
        }

        if(result == num) // check if the sum of cubes of each digits is equal to the number
            Systemout.println("Given number is an Armstrong number");.
        else
            System.out.println("Given number is not an Armstrong number");
    }
    
}

Output

Enter a number:370
Given number is an Armstrong number
Enter a number:134
Given number is not an Armstrong number