Write a program to accept a number and check whether it is a happy number or not.

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

for 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

so 28 is a happy number.

```
import java.io.*;
class Happy
{
public static void main()throws IOException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter a number");
int num=Integer.parseInt(br.readLine());
int sum=0;
double a=0;
while(num>=0)
{
a=num%10;
a=Math.pow(a,2);
sum+=a;
num=num/10;
if(num==0)
{
if(sum<10)
break;
else
{
num=sum;
sum=0;
continue;
}
}
}
if(sum==1)
System.out.println("It is a happy number");
else
System.out.println("It is a happy number");
}
}
```