public class XMLSalesFormatter implements SalesFormatter {
	static private XMLSalesFormatter singletonInstance
    = null;
	static public XMLSalesFormatter getSingletonInstance() {
		if (singletonInstance == null) {
            singletonInstance = new XMLSalesFormatter();
        }

        return singletonInstance;
	}
	private XMLSalesFormatter() {		
	}
	public String formatSales(Sales sales) {
		double totalCost=0.0;
		String string=new String();
		String NEW_LINE =System.getProperty("line.separator");
		string+=("<Sales>"+NEW_LINE);
		for(Order elementOne :sales) {
			for(OrderItem elementTwo :elementOne) {
				totalCost+=elementTwo.getValue();
			}
			string+=("<Order total=\""+totalCost+"\">"+NEW_LINE);
			for(OrderItem elementThere :elementOne) {
				string+=("  <OrderItem quantity=\""+elementThere.getQuantity()+
						 "\" price=\""+elementThere.getProduct().getPrice()+
						 "\">"+elementThere.getProduct().getCode()+
						 "</OrderItem>"+NEW_LINE);
			}
			string+=("</Order>"+NEW_LINE);
		}
		string+="</Sales>";
		return string;
	}

}