How do write an algorithm to print prime number ?

Problem statement:
Given a number n, print all primes smaller than or equal to n. It is also given that n is a small number.

Example:

Input : n =10 

Output : 2 3 5 7 

Input : n = 20 

Output: 2 3 5 7 11 13 17 19

1. public class PrimeNumberSeries {
2.     public static void main(String arg[]) {
3.         primeNumberSeries(10);
4.     }
5.     public static void primeNumberSeries(int n) {
6.         // Create a boolean array "prime[0..n]" and initialize all entries it as            //true. A value in prime[i] will finally be false if i is Not a prime, else true
7.         boolean prime[] = new boolean[n + 1];
8.         for (int i = 0; i < n; i++) {
9.             prime[i] = true;
10.         }
11.         for (int p = 2; p * p <= n; p++) {
12.             if (prime[p] == true) {
13.                 // update all multiple of p
14.                 for (int i = p * 2; i <= n; i = i + p) {
15.                     prime[i] = false;
16.                 }
17.             }
18.         }
19.         // print all prime numbers
20.         for (int i = 2; i <= n; i++) {
21.             if (prime[i] == true) {
22.                 System.out.print(i + " ");
23.             }
24.         }
25.     }
26. }

output:
2 3 5 7