Java Program for Sieve of Eratosthenes
Given a number n, print all primes smaller than or equal to n. It is also given that n is a small number.
For example, if n is 10, the output should be “2, 3, 5, 7”. If n is 20, the output should be “2, 3, 5, 7, 11, 13, 17, 19”.
Java
// Java program to print all primes smaller than or equal to // n using Sieve of Eratosthenes class SieveOfEratosthenes { void sieveOfEratosthenes( int n) { // 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. boolean prime[] = new boolean [n+ 1 ]; for ( int i= 0 ;i<=n;i++) prime[i] = true ; for ( int p = 2 ; p*p <=n; p++) { // If prime[p] is not changed, then it is a prime if (prime[p] == true ) { // Update all multiples of p for ( int i = p*p; i <= n; i += p) prime[i] = false ; } } // Print all prime numbers for ( int i = 2 ; i <= n; i++) { if (prime[i] == true ) System.out.print(i + " " ); } } // Driver Program to test above function public static void main(String args[]) { int n = 30 ; System.out.print( "Following are the prime numbers " ); System.out.println( "smaller than or equal to " + n); SieveOfEratosthenes g = new SieveOfEratosthenes(); g.sieveOfEratosthenes(n); } } // This code has been contributed by Amit Khandelwal. |
Output
Following are the prime numbers smaller than or equal to 29 2 3 5 7 11 13 17 19 23 29
Please refer complete article on Sieve of Eratosthenes for more details!