PrimesComputer.java

package primes;
import javax.inject.Singleton;
import java.util.stream.*;
import java.util.*;
@Singleton
public class PrimesComputer {
    private Random r = new Random(41);
    public List<Long> random(int upperbound) {
        int to = 2 + r.nextInt(upperbound - 2);
        int from = 1 + r.nextInt(to - 1);
        return primeSequence(from, to);
    }
    public static List<Long> primeSequence(long min, long max) {
    return LongStream.range(min, max)
            .filter(PrimesComputer::isPrime)
            .boxed()
            .collect(Collectors.toList());
    }
    public static boolean isPrime(long n) {
        return LongStream.rangeClosed(2, (long) Math.sqrt(n))
                .allMatch(i -> n % i != 0);
    }
}