sieve in java

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Erika
12 Jul 2020
1class SieveOfEratosthenes 
2{ 
3    void sieveOfEratosthenes(int n) 
4    { 
5        // Create a boolean array "prime[0..n]" and initialize 
6        // all entries it as true. A value in prime[i] will 
7        // finally be false if i is Not a prime, else true. 
8        boolean prime[] = new boolean[n+1]; 
9        for(int i=0;i<n;i++) 
10            prime[i] = true; 
11          
12        for(int p = 2; p*p <=n; p++) 
13        { 
14            // If prime[p] is not changed, then it is a prime 
15            if(prime[p] == true) 
16            { 
17                // Update all multiples of p 
18                for(int i = p*p; i <= n; i += p) 
19                    prime[i] = false; 
20            } 
21        } 
22          
23        // Print all prime numbers 
24        for(int i = 2; i <= n; i++) 
25        { 
26            if(prime[i] == true) 
27                System.out.print(i + " "); 
28        } 
29    } 
30      
31    // Driver Program to test above function 
32    public static void main(String args[]) 
33    { 
34        int n = 30; 
35        System.out.print("Following are the prime numbers "); 
36        System.out.println("smaller than or equal to " + n); 
37        SieveOfEratosthenes g = new SieveOfEratosthenes(); 
38        g.sieveOfEratosthenes(n); 
39    } 
40}