How To Check Whether a Number Is a Fascinating Number or Not in Java?

Fascinating number can be defined as a number which when multiplied with 2 and 3, and then the products after being concatenated with the number itself contains all the digits from 1 to 9.

For a number to be a fascinating number it should be three or more than three digit.

To show you some instances

Instance-1

Input number is 327

Let’s check it by using the logic of Fascinating number −

327 * 2 = 654
327 * 3 = 981

Concatenating “654” + “981” + “327” = 654981327

Hence, 327 is a Fascinating number.

Instance-2

Input number is 192

Let’s check it by using the logic of Fascinating number −

192 * 2 = 384
192 * 3 = 576

Concatenating “384” + “576” + “192” = 384576192

Hence, 327 is a Fascinating number.

Instance-3

Input number is 241

Let’s check it by using the logic of Fascinating number −

241 * 2 = 482
241 * 3 = 723

Concatenating “482” + “723” + “241” = 482723241

Hence, 241 is not a Fascinating number

Some other examples of fascinating numbers include 192, 1920, 2019, 327 etc.

Algorithm

• Step 1 − Get an integer number either by initialization or by user input.

• Step 2 − Check if that is a three-digit number.

• Step 3 − Multiply the number by 2 and 3.

• Step 4 − Concatenate both the products with the number itself.

• Step 5 − Now find If all the digits from 1 to 9 are present in the number. If it does then it is a fascinating number

Multiple Approaches

We have provided the solution in different approaches.

• By Using Static Input Value

• By Using User Defined Method

Let’s see the program along with its output one by one.

Approach-1: By Using Static Input Value

In this approach, initialize an integer value in the program and then by using the algorithm we can check whether a number is a Fascinating number or not.

Example

public class Main {

   public static void main(String args[]){   
      // Initialized an integer value
      int num = 327;
      System.out.println("Given number: "+num);

      // Store the product of the numbers in the variables
      int prod1 = num*2;
      int prod2 = num*3;

      // Concatenate the numbers
      String concatNum = prod1+""+prod2+num;
      // Boolean value to store the result
      boolean flag = true;

      // Loops from 1 to 9
      for(char c = '1'; c <= '9'; c++)  {  
         // COunt holds the number of times a digit occurs
         int count = 0;  
         //loop counts the frequency of each digit  
         for(int i = 0; i < concatNum.length(); i++)  {  
            char ch = concatNum.charAt(i);  
            //compares the character of concatNum with i  
            if(ch == c)  
            //increments the count by 1 if the specified condition returns true  
            count++;  
         }
         // Checks if all the digits are present in the number
         if(count > 1 || count == 0)  {  
            flag = false;  
            break;  
         }
      }  
      // Prints the result
      if(flag)
         System.out.println("Fascinating number");
      else
         System.out.println("Not a fascinating number");
   }
}   

Output

Given number: 327
Fascinating number

Approach-2: By Using User Defined Method

In this approach, initialize an integer value in the program and pass this number as a parameter in a user defined method then inside the method by using the algorithm we can check whether a number is a Fascinating number or not.

Example

public class Mai {
   static boolean fascinatingNum(int num){
      // Store the product of the numbers in the variables
      int prod1 = num*2;
      int prod2 = num*3;
      
      // Concatenate the numbers
      String concatNum = prod1+""+prod2+num;
      // Boolean value to store the result
      boolean flag = true;

      // Loops from 1 to 9
      for(char c = '1'; c <= '9'; c++)  {  
         // COunt holds the number of times a digit occurs
         int count = 0;  
         //loop counts the frequency of each digit  
         for(int i = 0; i < concatNum.length(); i++){  
            char ch = concatNum.charAt(i);  
            //compares the character of concatNum with i  
            if(ch == c)  
            //increments the count by 1 if the specified condition returns true  
            count++;  
         }
         // Checks if all the digits are present in the number
         if(count > 1 || count == 0)  {  
            flag = false;  
            break;  
         }
      }  
      return flag;
   }
   public static void main(String args[]){   
      // Initialized an integer value
      int num = 327;
      System.out.println("Given number: "+num);

      // Calls the user defined method and stores the result in res variable
      boolean res = fascinatingNum(num);

      // Prints the result
      if(res)
         System.out.println("Fascinating number");
      else
         System.out.println("Not a fascinating number");
   }
}

Output

Given number: 327
Fascinating number

In this article, we explored how to check a number whether it is a fascinating number or not in Java by using different approaches.