import Control.Monad
import Data.Array.Base
import Data.Array.IO
import System.Environment

sieve :: Int -> IO (IOUArray Int Bool)
sieve n = newArray (2, n-1) True >>= loop 2
  where loop i a = if i*i > n then return a else do
          p <- unsafeRead a i
          when p $ mapM_ (\j -> unsafeWrite a j False) [i*i, i*i+i..n-1]
          loop (succ i) a

main :: IO ()
main = do
  name <- getProgName
  getArgs >>= \args -> case args of
    [n] -> let n' = read n in sieve n' >>= \a -> mapM_ (printIfPrime a) [2..n'-1]
    _   -> putStrLn $ "usage: " ++ name ++ " N"
    where printIfPrime a i = unsafeRead a i >>= \p -> when p $ putStrLn (show i)

vs.

import java.util.Arrays;

public class Sieve {

    private static void printPrimes(boolean[] arr) {
        for (int i=2; i<arr.length; i++)
            if (arr[i])
                System.out.println(i);
    }

    private static boolean[] sieve(boolean[] arr) {
        for (int i=2; i*i <= arr.length; i++)
            for (int j=i*i; arr[i] && j < arr.length; j+=i)
                arr[j] = false;
        return arr;
    }

    public static void main(String[] args) {
        if (args.length != 1) {
            System.out.println("usage: java Sieve N");
            System.exit(1);
        }

        int n = Integer.parseInt(args[0]);
        if (n < 0) {
            System.out.println("abort (N < 0)");
            System.exit(1);
        }

        boolean[] a = new boolean[n];
        Arrays.fill(a, true);
        boolean[] primes = sieve(a);
        printPrimes(primes);

    }
}