# Java Program for Sieve of Eratosthenes

• Difficulty Level : Easy
• Last Updated : 05 May, 2021

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!

My Personal Notes arrow_drop_up
Recommended Articles
Page :