Armstrong Number Checking Program In BlueJ

What is Armstrong number?

From any number, the digits are to be separated and sum of the digit to the power number of digits of each digit is to be calculated. If the sum and number matches then the number is an Armstrong number.

For example if we enter 134 as the number then the number of digit in the number is 3. The sum would be 1^3+3^3+4^3 which is not equal to 134, so 134 is not an Armstrong number. Again if the number is 1234 then the sum would be 1^4+2^4+3^4+4^4. 153 is an Armstrong number as 1^3+5^3+3^3 equals to 153.

It is found that students always use 3 as the power but it is not correct way of checking Armstrong number although 3 digit numbers are Armstrong number only.

Codes of the Armstrong number checking program using 3 as power value

import java.io.*;
class Armstrong
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
int p,sum=0,c,spy=0,i;

public void takeData() throws IOException
{
System.out.println("Enter the number:-");
i=Integer.parseInt(br.readLine());
p=i;
while(p>9)
{
spy=1;
c=p%10;
sum=sum+(int)Math.pow(c,3);
p=p/10;
}
if(spy==1)
{
sum=sum+(int)Math.pow(p,3);
if(sum==i)
System.out.println(i+ " is amstrong number");
else
System.out.println("Not amstrong number.");
}
else
System.out.println("Not possible.");
}
public static void main(String args[])throws IOException
{
Armstrong obj=new Armstrong();
obj.takeData();
}
}

Now I will do the same program using number of digits of the number as power value.

Variable description of the Armstrong number checking program

BufferedReader br is used to take the number from user.
int p is a variable is used as loop control variable in this program.
int digit counts the number of digits in the entered number
int sum stores the sum of the digit to the power number of digits value.
int c holds the individual digits of the number.
int spy is used for checking purpose, whether the number is single digit or not.
int i holds the original number entered by user.

How to proceed in the program

Firstly the number is stored in variable ‘i’ and using do while loop the number of digits is counted and stored in variable ‘digit’.
The second do while loop is used to extract the digits of the number one by one and the power value is stored in the variable ‘sum’. At the end of the loop, values of ‘sum’ and the number is compared to reach the conclusion.

Modified codes of the same program on Armstrong number checking


import java.io.*;
class Armstrong
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
int p,digit=0,sum=0,c,spy=0,i;

public void takeNumber() throws IOException
{
System.out.println("Enter the number:-");
i=Integer.parseInt(br.readLine());
p=i;
do
{
digit++;
p=p/10;
}while(p!=0);
p=i;
do
{
spy=1;
c=p%10;
sum=sum+(int)Math.pow(c,digit);
p=p/10;
}while(p!=0);
if(spy==1)
{
if(sum==i)
System.out.println(i+ " is amstrong number");
else
System.out.println("Not amstrong number.");
}
else
System.out.println("Not possible.");
}
public static void main(String args[])throws IOException
{
Armstrong obj=new Armstrong();
obj.takeNumber();
}
}

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