Question

if we retrieve value from Map and then we do some changes ,
so we again need to put that object back on Map

for ex

       Human human  = (Human ) domainObjects
            .get(Constants.Human;
       human.setName("Vish");

   domainObjects.put(Constants.Human, human);

Or as we are passing the reference of object,the changes will be also present in the domain object even without using Map put function

Answer 1

Map returns a copy of a reference to the underlying object. Not a copy of the object. When you call setName you are changing the object.

It would appear you should be using enums for you Constants or plain classes.

Map<EnumType, Object> map = new EnumMap<EnumType, Object>(EnumType.class);
Human human = (Human) map.get(EnumType.Human);

or

Map<Class, Object> map = new LinkedHashMap<Class, Object>();
Human human = (Human) map.get(Human.class); // no need for a constant.