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

Bouncy number can be defined as a positive number whose digits do not follow increasing or decreasing order.

Means the digits are in an unsorted manner.

There are no bouncy numbers between 1 to 100.

To show you some instances

Instance-1

Input number is 101

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

1 > 0 and 0 < 1

Hence, 101 is a Bouncy number.

Instance-2

Input number is 905

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

9 > 0 and 0 < 5

Hence, 905 is a Bouncy number.

Instance-3

Input number is 245

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

2 < 4 but 4 < 5 means all digits are in decreasing order.

Hence, 245 is not a Bouncy number.

Some other examples of Bouncy numbers include 102, 564,897 etc.

Syntax

We can convert integer value to String value by using inbuilt toString() method.

Following is the syntax for that.

String str = Integer.toString(inputNumber)

We can pick a character at any index from a string using charAt( ) method. Following is the syntax for that.

char ch = str.charAt(0);

Algorithm

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

• Step 2 − Set flag to true and check if the digits are in ascending or descending order

• Step 3 − If the digits follow ascending or descending order set flag to false.

• Step 4 − Print the result.

Multiple Approaches

We have provided the solution in different approaches.

• By Using Static Input Value

• By Using User Defined Method and with charAt( ) Method

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

Approach-1: By Using Static Input Value

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

Example

import java.util.*;

public class Main{
   //Main method
   public static void main(String args[]){   

      //initialized a number
      int num = 6549;
      
      //printing the given number
      System.out.println("Given number: "+num);

      // Checks if the number is less than 100
      if(num<100){
         System.out.println("The number is not a bouncy number");
      }

      // Boolean values to check if the digits are sorted
      boolean increasing = true, decreasing = true;

      // Storing the number in a temporary variable and storing the first digit
      int temp = num, prev = num % 10;

      // Loops until the number becomes zero
      while(temp != 0){

         // Checks if it follows increasing order or not
         if(temp%10>prev){
            increasing = false;
            break;
         }

         // Gets the last digit of the number
         prev = temp % 10;

         // Removes the last digit
         temp /= 10;
      }

      // Resets the value
      temp = num;
      prev = num % 10;

      while(temp != 0){
         // Checks if it follows decreasing order or not
         if(temp%10<prev){
            decreasing = false;
            break;
         }

         // Gets the last digit of the number
         prev = temp % 10;

         // Removes the last digit
         temp /= 10;
      }

      // Prints the result
      if(!increasing&&!decreasing)
         System.out.println("The number is a bouncy number");
      else
         System.out.println(", The number is not a bouncy number");
   }
}

Output

Given number: 6549
The number is a bouncy number

Approach-2: By Using User Defined Method and With charAt() Method

In this approach, the user will be asked to take the input of an integer value 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 Bouncy number or not.

Example

public class Main{
   // Checks if the digits are in increasing order
   static boolean isIncreasing(int num){

      // Converts the number to a string
      String s = Integer.toString(num);
      char dig;
      boolean result = true;

      // Loops over all the digits
      for(int i = 0; i < s.length()-1; i++){
            
         // Stores the digit at i th location
         dig = s.charAt(i);
            
         // Compares the digit with its next location
         if(dig > s.charAt(i+1)){

            // Sets the result to false and breaks out of the loop
            result = false;
            break;
         }
      }
      return result;
   }

   // Checks if the digits are in decreasing order
   static boolean isDecreasing(int num){

      // Converts the number to a string
      String s = Integer.toString(num);
      char dig;
      boolean result = true;

      // Loops over all the digits
      for(int i = 0; i < s.length()-1; i++){

         // Stores the digit at i th location
         dig = s.charAt(i);

         // Compares the digit with its next location
         if(dig < s.charAt(i+1)){

            // Sets the result to false and breaks out of the loop
            result = false;
            break;
         }
      }
      return result;
   }
   //user defined method to check bouncy number
   static boolean bouncyNum(int num){

      // Checks if the number is less than 100
      if(num<100){

         System.out.println("The number is not a bouncy number");
      }
      // Checks for sorted digits using the functions
      if(!isIncreasing(num)&&!isDecreasing(num))
         return true;
      else
         return false;
   }
   //main method
   public static void main(String args[]){ 
  
      //initialized a number
      int num = 150;

      //printing the given number
      System.out.println("Given number: "+num);

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

      // Prints the result
      if(res)
         System.out.println("The number is a bouncy number");
      else
         System.out.println("The number is not a bouncy number");
   }
}

Output

Given number: 150
The number is a bouncy number

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