program logic of printing the prime numbers

Question

Can any body help to understand this java program?

It just prints prime numbers, as you enter how many you want and it works well.

class PrimeNumbers
{           


        

Answer 1

If I'm right there is a theory in math, saying that nearly all prime numbers can be determined when checking numbers from 2 to square root of n instead of checking all numbers from 2 to n oder 2 to n/2.