Paste code

import java.util.Scanner;

public class Primzahlen 
{
 /**
  * Main
  * @param args
  * @return Primzahl
  */
 public static void main(String[] args) 
 {
  double startZeit = System.currentTimeMillis();
  
  int x, thePrime = 0, j = 2;
  
  System.out.print("Bitte geben Sie die n-te Primzahl ein: ");
  
  Scanner get;
  get = new Scanner(System.in);
  x = get.nextInt();
  
  int counter = 0;
  while(j <= x*x)
  {
   if(primetest(j))
   {
    thePrime = j;
    counter++;
   }
   j++;
   if(counter == x)
   {
    break;
   }
   
  }
  System.out.println(thePrime);
  System.out.println("Zeit dauer: "+ (System.currentTimeMillis()-startZeit) + " millisekunden");
 }
 
 /**
  * Prueft ob es eine Primezahl ist.
  * @param int prime
  * @return boolean
  */
 public static boolean primetest(int prime)
 {
  int p = 0;
  
  for(p = 2; p < prime; p++)
  {
   if(prime % p == 0)
   {
    return false;
   }
  }
  return true;
 }
}