Please find below logic which will help you to write most optimized way to find if a number is Prime or not.
What is Prime Number ?
A number that is divisible only by itself and 1 (e.g. 2, 3, 5, 7, 11).
BEST Coding Practice
It’s always preferable as Best Coding Practice to write a method instead of writing anywhere in the Class to create a reusable code.
boolean isPrime(int num) { if ( n % 2 == 0 ) return false; for ( int i=3; i*i < n, i += 2) { if ( n % i == 0 ) return false; } return true; }