How To Check Whether a Number is an Ugly Number or Not in Java?

A number is said to be an ugly number, if the prime factors of that input number only include 2, 3 and 5.

Maybe some number has some prime factors which have only one factor or two factors but those factors must be one of 2, 3, and 5.

In this article we will see how to check if a number is an Ugly number or not by using Java programming language.

To show you some instances

Instance-1

Input number is 20.

Let’s check it by using the logic of Ugly number.

Prime factors of 20 = 2, 2, 5

So, as you notice here all the prime factors include either of 2, 3 and 5 only.

Hence, 20 is an ugly number.

Instance-2

Input number is 30.

Let’s check it by using the logic of Ugly number.

Prime factors of 30 = 2, 3, 5

So, as you notice here all the prime factors include either of 2, 3 and 5 only.

Hence, 30 is an ugly number.

Instance-3

Input number is 14.

Let’s check it by using the logic of Ugly number.

Prime factors of 14 = 2, 7

So, as you notice here 7 is present at one of the prime factors above.

Hence, 14 is not an ugly number.

Algorithm

• Step 1 − First we define a function for checking if the input number is a prime number or not.

• Step 2 − Collect the input from the user either by static method or by user defined method.

• Step 3 − Initialise the loop for finding all the prime factors of input number.

• Step 4 − After find the prime factor we run a condition for checking whether the factors have only included 2, 3, and 5 or not.

• Step 5 − If the condition is true then we are printing the input number is an ugly number otherwise the input number is not an ugly 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 Java program along with its output one by one.

Approach-1: By Using Static Input Value

In this approach one non−zero, positive integer value will be initialized in the program and then by using the algorithm we can check whether a number is an ugly number or not.

Example

import java.util.Scanner;
public class Main {
   public static void main(String args[]) {

      //declare a variable with a static value
      int inputNumber = 25;

      //declare a variable with boolean value
      boolean check = true;

      //initialise the loop for the checking of ugly number
      for(int i = 2; i<=inputNumber; i++) {

      // checks whether numbers only include 2,3 and 5
         if(i!=2&&i!=3&&i!=5) {

         // Checks if there are some other prime factors
            if(inputNumber%i==0&&checkPrime(i)) {

            // Sets the flag to false if there are some other prime factors
               check = false;
               break;
            }

         }
      }
      if(check) {
         System.out.println(inputNumber+" is an ugly number");
      } else {
         System.out.println(inputNumber+" is Not an ugly number");
      }
   }

   // Function that checks for prime
   static boolean checkPrime(int number) {
      boolean flag = true;
      for(int i = 2; i<=number/2; i++) {
         if(number%i==0) {
            flag = false;
            break;
         }
      }
      return flag;
   }
}

Output

25 is an ugly number

Approach-2: By Using User Defined Method

In this approach one non−zero, positive integer value will be initialized in the program and then we will call a user defined method by passing this input number as parameter.

Inside the method we will check whether a number is an ugly number or not by using the algorithm.

Example

import java.util.Scanner;
public class Main {
   //initialise main method
   public static void main(String[] args) {

      //declare a variable with a static value
      int inp = 56;

      //check whether our condition is true or not in user defined method
      //if true number is ugly otherwise not
      if(checkUgly(inp)) {
         System.out.println(inp+" is an ugly number");
      } else {
         System.out.println(inp+" is Not an ugly number");
      }

   }
   // Function that checks for prime
   static boolean checkPrime(int number) {
      boolean flag = true;
      for(int i = 2; i<=number/2; i++) {
         if(number%i==0) {
            flag = false;
            break;
         }
      }
      return flag;
   }

   //define the user defined method
   //checking for ugly number
   public static boolean checkUgly(int inputNumber) {

      //declare a variable with boolean value
      boolean check = true;

      //initialise the loop for the checking of Ugly number
      for(int i = 2; i<=inputNumber; i++) {

         // checks whether numbers only include 2,3 and 5
         if(i!=2&&i!=3&&i!=5) {

            // Checks if there are some other prime factors
            if(inputNumber%i==0&&checkPrime(i)) {

               // Sets the flag to false if there are some other prime factors
               return false;
            }

         }
      }
      return true;
   }
}

Output

56 is Not an ugly number

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