// concurrent/ParallelPrime.java
// (c)2017 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.util.*;
import java.util.stream.*;
import static java.util.stream.LongStream.*;
import java.io.*;
import java.nio.file.*;
import onjava.Timer;

public class ParallelPrime {
 static final int COUNT = 100_000;
 public static boolean isPrime(long n) {
 return rangeClosed(2, (long)Math.sqrt(n))
 .noneMatch(i -> n % i == 0);
 }
 public static void main(String[] args)
 throws IOException {
 Timer timer = new Timer();
 List<String> primes =
 iterate(2, i -> i + 1)
 .parallel() // [1]
 .filter(ParallelPrime::isPrime)
 .limit(COUNT)
 .mapToObj(Long::toString)
 .collect(Collectors.toList());
 System.out.println(timer.duration());
 Files.write(Paths.get("primes.txt"), primes,
 StandardOpenOption.CREATE);
 }
}
/* Output:
1224
*/