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import java.util.concurrent.BlockingQueue;
import java.util.concurrent.SynchronousQueue;

public class Primes {

    BlockingQueue<Integer> generateIntegers() {
	final BlockingQueue<Integer> q = new SynchronousQueue<Integer>();

	new Thread() {
	    @Override
	    public void run() {
		for (int i = 2; true; i++) {
		    try {
			q.put(i);
		    } catch (InterruptedException e) {
			e.printStackTrace();
			System.exit(1);
		    }
		}
	    }
	}.start();

	return q;
    }

    BlockingQueue<Integer> filterMultiples(final BlockingQueue<Integer> in,
	    final int prime) {
	final BlockingQueue<Integer> out = new SynchronousQueue<Integer>();

	new Thread() {
	    @Override
	    public void run() {
		while (true) {
		    try {
			int i = in.take();
			if (i % prime != 0) {
			    out.put(i);
			}
		    } catch (InterruptedException e) {
			e.printStackTrace();
			System.exit(1);
		    }
		}
	    }
	}.start();

	return out;
    }

    BlockingQueue<Integer> sieve() {
	final BlockingQueue<Integer> out = new SynchronousQueue<Integer>();

	new Thread() {
	    @Override
	    public void run() {
		BlockingQueue<Integer> q = generateIntegers();
		while (true) {
		    try {
			int prime = q.take();
			out.put(prime);
			q = filterMultiples(q, prime);
		    } catch (InterruptedException e) {
			e.printStackTrace();
			System.exit(1);
		    }
		}
	    }
	}.start();

	return out;
    }

    public static void main(String[] args) {
	BlockingQueue<Integer> primes = new Primes().sieve();

	while (true) {
	    try {
		System.out.println(primes.take());
	    } catch (InterruptedException e) {
		e.printStackTrace();
		System.exit(1);
	    }
	}
    }
}