Java Program to Print Prime Numbers upto n (Optimised)

//Reading an integer & printing prime numbers upto that integer
import java.io.*;
import java.util.Scanner;
import java.lang.Math;
class Prime{
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        int n =sc.nextInt();
        int i;
        for(i = 2;i <= n; i++){
            if(isprime(i) == 1){
                System.out.print(i+" ");
            }
        }
        sc.close();
    }
    static int isprime(int n){
        int i;
        if(n==0 || n==1){
            return(0);
        }
        if(n==2||n==3){
            return(1);
        }
        if(n%2==0||n%3==0){
            return(0);
        }
        for(i=5;i<Math.sqrt(n);i+=6){
            if(n%i==0||n%(i+2)==0){
                return(0);
            }
        }
        return(1);
    }
}

 Output:

25
2 3 5 7 11 13 17 19 23