36 lines
1020 B
Java
36 lines
1020 B
Java
// concurrent/ParallelPrime.java
|
|
// (c)2020 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
|
|
*/
|