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# 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!

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