Design patterns

Safe Getters and Setters

-domain objects returning collection objects in getter should check for null

and return EMPTY_COLLECTION instead of null collection

-domain objects returning string objects in getter should check for null and

return empty string instead of null

Assert methods to validate method arguments

-call assert methods to check for null arguments instead of checking objects for null and throwing an IllegalArgumentException

-in graph of objects add getter methods to link child objects to parent objects

Null object Design pattern

-to avoid checking for null across the whole application. centralize the null checks within domain object, service object getters