public boolean isSubSetOf(IntegerSet other) {
	  
	  int i = 0;
	  boolean isSubSet = true;
	  
	  other.removeDuplicates();
	  this.removeDuplicates();
	  
	    while (i < this.elements.size()) {
	        Integer item = this.elements.get(i);
	        int j = 0;
	        boolean elementInSet = false;
	        
	        while (j < elements.size()) {
	          if (item.equals(other.elements.get(j))) {
	            elementInSet = true;
	          }
	          j++;
	        }
	        
	        if (!elementInSet) {
	         isSubSet = false;
	        }
	        
	        i++;
	   }
	    
	   return isSubSet;
  }