Prime Number Generator Logic

Question

I am supposed to make a class PrimeNumberGenerator which has a method nextPrime that will print out all prime numbers up to a number the user input

Answer 1

I know the question is for a while out here but since no one posted java8/stream approach solution, here is one of the possible ways.

Gist can be forked here.

Print output: [1, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71]

import java.util.*;
import java.util.stream.Stream;

import static java.util.stream.Collectors.toList;


public class PrimeNumber {

     /**
     * Java 8 / Lambda approach to generate Prime number.
     * Prime always start to look from number 1.
     * @param series Number of how many Prime number should be generated
     * @return List holding resulting Prime number.
     */
    public static List generate(int series) {
        Set set = new TreeSet<>();
        return Stream.iterate(1, i -> ++i)
                .filter(i -> i %2 != 0)
                .filter(i -> {
                    set.add(i);
                    return 0 == set.stream()
                            .filter(p -> p != 1)
                            .filter(p -> !Objects.equals(p, i))
                            .filter(p -> i % p == 0)
                            .count();
                })
                .limit(series)
                .collect(toList());
    }

    // Let's test it!
    public static void main(String[] args) {
        List generate = PrimeNumber.generate(20);
        System.out.println(generate);
    }
}