Implement Sieve of Eratosthenes - Java Algorithm

Java examples for Algorithm:Number

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Description

Implement Sieve of Eratosthenes

Demo Code


public class Sieve_of_Eratosthenes 
{
  public static void output(int n) 
  {//w  w  w  . ja va 2  s . co m
    boolean prime[] = new boolean[n+1]; // All the elements of array initialized as false by default
    
    // If i is non-prime, change prime[i] to true
    for(int p = 2; p*p <= n; p++)
    {
      if(!prime[p]) // If prime[p] is still false, then p is a prime
      {
        for(int i = p*2; i <= n; i += p) // Update all multiples of p as they are non-prime
        prime[i] = true;
      }
    }
    // Print all prime numbers
    for(int i = 2; i < prime.length; i++)
    {
      if(prime[i] == false) // Finally, elements which are still false are those whose location is prime 
      System.out.print(i + "  "); // Printing these prime location
    }
  }
  
  // Driver function to test above function
  public static void main(String[] args) 
  {
    int n = 30;
    System.out.println("Following are the prime numbers smaller than or equal to " + n);
    output(n);
  }
  
}

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