title: want to make a program that selects out prime numbers. don't get why my program doesn't work
body: <p>whenever I try to run this program, it first shows "The prime's upper bound?" After inserting an integer and pressing enter, I don't see anything then. I want it to display some "false" values, but I can't find where the problem is. And the Java doesn't show where the problem is.</p>
  
  <pre><code>import java.util.Scanner;
  
  public class Lab11 {
  
      static int n;
      boolean [] primedetermine = new boolean [n];
      int [] list;
  
      public static void main (String[]args) {
          Scanner in = new Scanner (System.in);
          System.out.print ("The prime's upper bound? ");
          int max = in.nextInt();
          boolean prime [] = new boolean [max];
          computePrimes (prime);
      }
  
      public static void computePrimes(boolean[] primedetermine) {
          for (int x = 0; x&lt;n; x++) {
              primedetermine [x] = false;
          }
          for (int prm = 2; prm &lt;= n; prm++) {
              for (int prm2 = 2; prm * prm2 &lt;= 21; prm++) {
                  primedetermine [prm * prm2 -1] = true;
              }
          }
          for (int x = 1; x&lt;=n; x++){
              if (primedetermine[x-1] == false);
                  System.out.println(primedetermine[x-1]);
              }
          }
      }   
  }   
  </code></pre>