java - return an array of prime numbers -

i need method return prime numbers in array.

so if given: primearray(5)

than array should returned: (2, 3, 5)

for reason doesn't seem work me:

public static int[] primearray(int numfind) {     //determines size of array returned     int primetotal = 0;      //loop find total prime numbers     (int j = 1; j <= numfind; j ++)     {         if (isprime(j))         primetotal +=1;     }      //declare array returned     int[] numa = new int[primetotal];      //current index of prime number     int ip = 0;      //loop add prime elements array     (int x = 1; x <= numfind; x ++)     {         if (isprime(x))         {             numa[ip]=x;             ip++;    // <--- causing me problems         }      }      return numa; }  public static boolean isprime(int n) {     (int = 2; < n; i++)     {         if(n%i==0)             return false;     }     return true; } 

this i'm using test code:

    int[] num = primearray(11);      system.out.println(num[0]);     system.out.println(num[1]); 

but output i'm getting this:

1  2 

if comment out ip++; if statement decides execute when prime numbers passed parameter in: isprime(j) if defeats whole purpose of primearray method because need primearray method return array of prime numbers.

your isprime() method faulty. need return false, number < 2. also, don't need iterate till n, iterate till n / 2 or better sqrt(n).

change to:

public static boolean isprime(int n) {      if (n < 2) return false;      int maxiteration = math.ceil(math.sqrt(n));      (int = 2; < maxiteration; i++) {         if(n % == 0)             return false;     }      return true; } 

now, given real problem (note method fine. return correct result, given changed isprime() method), can avoid iterating twice using arraylist instead of array:

list<integer> primes = new arraylist<integer>();  //loop find total prime numbers (int j = 1; j <= numfind; j ++) {     if (isprime(j))         primes.add(j); } 

and can return primes, , change return type of method list<integer> instead of int[].

public static list<integer> primenumberlist(int numfind) 

if want return int[], need work converting arraylist int array. leave task you. search on only, many posts.

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also, if going generate prime numbers till large number, should take @ sieve of eratosthenes