// threads/Prime.java

// (c)2016 MindView LLC: see Copyright.txt

// We make no guarantees that this code is fit for any purpose.

// Visit http://mindviewinc.com/Books/OnJava/ 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 java.nio.charset.*;

public class Prime {

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 {

long start = System.currentTimeMillis();

List<String> primes =

iterate(2, i -> i + 1)

.parallel() //(1)

.filter(Prime::isPrime)

.limit(COUNT)

.mapToObj(Long::toString)

.collect(Collectors.toList());

System.out.println(

System.currentTimeMillis() - start);

Files.write(Paths.get("primes.txt"), primes,

StandardOpenOption.CREATE);

}

}