ingen dubletter

Jeg har et problem med at denne klasse skulle lave points der ikke overlapper hianden men det sker af og til at det sker hvad er der galt med koden, det er altså sådan at food ikke må have den samme point som wall

import java.util.*;
import java.awt.*;

public class MapBuilder    {

  private static Vector shared;


public static Vector buildLevel1()    {
   
    shared = new Vector();
    Vector res = new Vector();
    int i,j;
    for(i = 100,j = 50;j < 200 ;j += 5)    {
     
        Point p = new Point(i,j);
        Wall w = new Wall(p,0);
        res.add(w);
       
    }
   
    for(i = 200,j = 50;j < 200 ;j += 5)    {
     
        Point p = new Point(i,j);
        Wall w = new Wall(p,0);
        res.add(w);
        shared.add(w);
    }
   

  return res;
 
}



public static Vector buildLevel1FoodItems()      {

int[] range = new int[80];
Vector v = new Vector();

int i,j;
for(i=0,j = 0;j < range.length;i +=5,j++)    {
    range[j] = i;
    System.out.println(range[j]);
}
 
  int random = randomInt(0,80);
 
  i = 0;
  while (i < 5)  {
 
  if (i == -1)  {  i = 0;  }
 
  int x = range[randomInt(5,40)];
  int y = range[randomInt(5,40)];
 
  Point p = new Point(x,y);
 
  Food mapfood = new Food(p,10); 

 
  boolean found = false;
 
  for(j = 0;j < shared.size() && !found;j++)    {
   
    Wall w = (Wall)shared.elementAt(j);
   
   
    Point wallPoint = w.getPosition();
   
    if (p.x == wallPoint.x && p.y == wallPoint.y)  {
      found = true;
    }//end if
   
  }//end for
 
    if (!found)  {
      v.add(mapfood); i++; }
 
    else {
      i--; 
    }
 
 
 
}//end while
 
 
  return v;
 
}




public static int randomInt(int a, int b)    { 
 
  if (a > b) throw new IllegalArgumentException();
      if (a == b) return a;
      double x = Math.random();
      int n = a + (int)(x * (b - a + 1));
      if (n > b) n = b;
      return n;
  }//end randomInt
   

}//end mapBuilder