Question

A happy number is a number in which the eventual sum of the square of the digits of the number is equal to 1.

Example: 

28 = (2)² + (8)² = 4 + 64 = 68 

68 = (6)² + (8)² = 36 + 64 = 100 

100 = (1)² + (0)² + (0)² = 1 + 0 + 0 = 1

Hence, 28 is a happy number. 

Example: 1² = (1)² + (2)² = 1 + 4 = 5

Hence, 12 is not a happy number. 

Design a class Happy to check if a given number is a happy number. Some of the members of the class are given below: 

Class name: Happy 

Data Members/instance variables: 

n: stores the number Member functions 

Happy( ): constructor to assign 0 to n.

void getnum (int nn): to assign the parameter value to the number n = nn. 

int sum_sq_digits (int x): returns the sum of the square of the digits of the number x, using the recursive technique 

void is happy (): checks if the given number is a happy number by calling the function sum_sq_digits(int) and displays an appropriate message. 

Specify the class Happy giving details of the constructor (), void getnum (int), int sum_sq_digits (int) and void ishappy (). 

Also define a main ( s) function to create an object and call the methods to check for happy number.

Answer 1

class Happy 

{ 

int n, s, d; 

public Happy() { n = 0; 

} 

void getnum (int nn) 

{ 

n = nn, 

} 

int sum_sq_digits(int x) 

{ 

if (x > 0) 

{ 

d = x%10; 

s = s + d*d;

x = x/10; 

return (sum_sq_digits (x)); 

} 

else { returns; 

} 

} 

void ishappy () 

{ 

int a;

while (n > 9) 

{ 

s = 0; 

n = sum_sq_digits(n): 

} 

if (n== 1) 

System.out.println("Happy No.");

else System out.println("Not a Happy No."); 

}

}