int n=5,k=3;
     int[] numbers = new int[n];
      for (int i = 0; i < numbers.length; i++)
         numbers[i] = i + 1;
      int[] result = new int[k];
      for (int i = 0; i < result.length; i++)
      {
         // make a random index between 0 and n - 1
         int r = (int) (Math.random() * n);
         result[i] = numbers[r];
         numbers[r] = numbers[n - 1];
         n--;
      }

      // print the sorted array
      Arrays.sort(result);
      for (int r : result)
         System.out.println(r);