public boolean isValid(){
		// 1. do bound check on pts value
		if(this.width <= 0 || this.height <= 0 || this.no_of_division <= 0 ){
			return false;
		}
		
		// 2. do bound check on points to be removed.
		if(this.removalList != null){
			for(Point pt : removalList){
				if(pt.getX() < 0 || pt.getX() >= width ||
						pt.getY() < 0 || pt.getY() > height){
					return false;
				}
			}
			
		}
		
		return true;
	}