Ytukyg

I have a problem and the title actually sums it up perfectly. So i'll just go ahead and show you the code snippet.
So the methode generate, is generating an array, that is filled with numbers between 1 and 1000, including both. The length of the array is user input.
The next method, isPrime, is gonna conclude if its a prime number, so i can use those numbers with the true condition in another method. The generate method works but in isPrime i always get errors. If u can think of a better way, let me know please.

static int generate(int n) {

    int arr = new int[n+1];

    for(int x = 0; x <= n; x ++) {

        int number = (int) (Math.random()* 999)+1;

        arr[x] = number;

    }

    return arr;

}



static int isPrime(int p, final int q) {                           

    boolean itIs = true;

    //final int arr;



    for(int r = 0; r <= p; r++) {               // here it somehow states r is deadCode

        for(int j = 2; j < q[r]; j++) {             

            if(q[r]%j == 0) {                       

                itIs = false;                       

            }

        }

        return q[r];

    }



}

First, create a method to check a value is prime:

public boolean isPrime(int value) {

    for (int i = 0; i < value / 2; i++) { // value / 2 is enough, doesn't need to check all values

        if (value % i == 0) {

            return false;

        }

    }

    return true;

}

Then you check each value of array and put prime value to new array:

public int filterArray(int array) {

    List<Integer> intList = new ArrayList<>();

    for (int i = 0; i < array.length; i++) {

        if (isPrime(array[i])) {

            intList.add(array[i]);

        }

    }

    Integer integerArray = intList.toArray(new Integer[intList.size()]);

    int intArray = ArrayUtils.toPrimitive(integerArray);

    return intArray;

}

Then you get the filtered prime array.

It still doesn't work but i changed it to this.

static int generate(int n) {

    int arr = new int[n+1];

    for(int x = 0; x <= n; x ++) {

        int number = (int) (Math.random()* 999)+1;

        arr[x] = number;

    }

    return arr;

}





static boolean isPrime(int p) {                                     

    boolean itIs = true;

        for(int j = 2; j < p; j++) {                                

            if(p%j == 0) {                                          

                itIs = false;                                       

            }

        }   

    System.out.print(p + "bla" + itIs);

    return itIs;

}



//numberCount, isPrime, generate()

static void filterPrimeNumbers(int zahlmenge,boolean t, final int u) {

    int arr2 = new int[0];

    int l = 0;

    for(int n = 0; n <= zahlmenge; n++) {

        if(t) {

            arr2[l] = u[n];

            l++;

        }

        System.out.println(arr2[0]);

    }



}



public static void main(String args) {



    System.out.print("Give me a number: ");

    Scanner sc = new Scanner(System.in);

    int numberCount = sc.nextInt();

    filterPrimeNumbers(numberCount, isPrime(generate(numberCount)[0]), generate(numberCount));



}

}