Method to calculate warehosue overflow.

src/engine/objects/Warehouse.java

@@ -642,10 +642,14 @@ public class Warehouse {
 
     public static HashMap<mbEnums.ResourceType, Integer> calcOverflow(Warehouse warehouse, HashMap<mbEnums.ResourceType, Integer> cost_map) {
 
+        // Method returns a map of resourceType that a transaction overdrafts.
+
         HashMap<mbEnums.ResourceType, Integer> overflowMap = new HashMap<>();
 
         for (mbEnums.ResourceType resourceType : cost_map.keySet()) {
+
             int debit = warehouse.resources.get(resourceType) - cost_map.get(resourceType);
+
             if (debit < 0)
                 overflowMap.put(resourceType, debit);
         }