Spy Number in Java

In this section, we will learn what is a spy number and also create Java programs to check if the given number is Spy or not. The spy number program is frequently asked in Java coding test.

Spy Number

A positive integer is called a spy number if the sum and product of its digits are equal. In other words, a number whose sum and product of all digits are equal is called a spy number.

Example of Spy Number

Let's take the number 1124 and check whether the number is a spy or not. First, we will split it into digits (1, 1, 2, 4). After that find the sum and product of all the digits.

Sum=1+1+2+4=8

Product=1*1*2*4=8

We observe that the sum and product of the digits both are equal. Hence, 1124 is a spy number.

Similarly, we can check other numbers also. Some other spy numbers are 22, 123, 132, etc.

Steps to Find Spy Number

Read or initialize a number (n) that you want to check.
Declare two variables sum and product to store sum and product of digits. Initialize sum with 0 and product with 1.
Find the last digit (n%10) of the given number by using the modulo operator.
Add the last digit to the variable sum.
Multiply the last digit with the product variable.
Divide the given number (n) by 10. It removes the last digit.
Repeat steps 3 to 6 until the given number (n) becomes 0.
If the variable sum and product have the same value, then the given number (n) is a spy number, else not a spy number.

Let's implement the above steps in a Java program.

Spy Number Java Program

SpyNumberExample1.java

import java.util.Scanner;
public class SpyNumberExample1 
{
public static void main(String args[])
{ 
int num, product=1, sum=0, lastdigit;
// create object of scanner
Scanner sc = new Scanner(System.in);
System.out.print("Enter the number to check: " );
//reads an integer from the user and stores it in the variable num
num=sc.nextInt();
//executes untill the condition becomes false
while(num>0)
{
//finds the last digit of the number    
lastdigit=num%10;
//adds last digit to the variable sum
sum=sum+lastdigit;
//calculates the product
product=product*lastdigit;
//removes the last digit from the given number
num=num/10;
}
//compares the sum and product
if(sum==product)
//prints if the above condition returns true
System.out.println("The given number is a spy number.");
else
//prints if the above condition returns false
System.out.println("The given number is not a spy number.");
}
}

Output 1:

Enter the number to check: 123
The given number is a spy number.

Output 2:

Enter the number to check: 456
The given number is a not spy number.

SpyNumberExample2.java

import java.util.Scanner;
public class SpyNumberExample2
{
//method to check the Spy number
private static boolean isSpyNumber(int number) 
{
int lastDigit = 0;
int sum = 0;
int product = 1;
//executes until the condition returns true
while(number != 0) 
{
//determines the last digit of the given number
lastDigit = number % 10;
//adds the last digit to the variable sum
sum = sum + lastDigit;
//multiply last digit with product
product = product * lastDigit;
//removes the last digit of the given number
number = number / 10;
}
//compares the variable sum with product and returns the result accordingly
if(sum == product)
return true;
return false;
}
//driver code
public static void main(String args[]) 
{
int lowerRange = 0, upperRange = 0;
Scanner sc = new Scanner(System.in);
System.out.print("Enter the lower range: ");
//reads lower range
lowerRange = sc.nextInt();
System.out.print("Enter upper range: ");
//reads the upper range 
upperRange = sc.nextInt();
System.out.println("The Spy numbers between "+ lowerRange + " to "+ upperRange+" are: ");
for(int i=lowerRange; i<=upperRange; i++) 
{
//calling user-defined function that checks if the given number is spy or not
if(isSpyNumber(i))
//prints all the spy numbers
System.out.print(i +" ");
}
}
}

Output:

Enter the lower range: 1
Enter upper range: 10000
The Spy numbers between 1 to 10000 are: 
1 2 3 4 5 6 7 8 9 22 123 132 213 231 312 321 1124 1142 1214 1241 1412 1421 2114 2141 2411 4112 4121 4211

Next TopicTypes of Applets in Java

← prev next →