Print prime values contained in an array

Question

I can’t get the prime numbers that are inside this List4 array; I’ve tried several ways, but without success. Currently, my code looks like this:

List<Integer> list8 = new ArrayList<>();
    int numPrimo = 0;
            int numDivisores = 0;
            for (int i = 1; i <= list4.size(); i++) {
                if (numPrimo % i == 0) {
                    numDivisores++;
                }
                if(numDivisores == 2) {
                    list8.add(numDivisores);
                }
            }
            sysout("10) Os números primos entre as duas listas são: " + list8);

I need a light

Answer 1

You need to do a for to list all the elements of the list 4 and, within that, create a new loop to check if the number in question is a prime number (increasing the number of divisors). After this second loop, you can check if the number of divisors is equal to 2, ie if the number is prime. Follow the code:

public static void main(String[] args) {

    List<Integer> list8 = new ArrayList<Integer>();
    List<Integer> list4 = new ArrayList<Integer>();

    for(int i = 0; i < 10; i++) {
        list4.add(i);
    }

    int numDivisores = 0;

    for (Integer numPrimo : list4) {
        for (int i = 1; i <= numPrimo; i++) {
            if (numPrimo % i == 0) {
                numDivisores++;
            }
        }

        if (numDivisores == 2) {
            list8.add(numPrimo);
        }
        numDivisores = 0;
    }

    System.out.println("10) Os números primos entre as duas listas são: " + list8);
}