To use the interface creating a container

Question

Hello,
I read around that is normal thing write Set<String> set = new HashSet<String>() in place of HashSet<String> set = new HasSet<String>(); I read the same with other containers too (Map = new HashMap, List = new ArrayList). I don't understand the real importance. Moreover, If I got something right, the interface "could" not have "few" method of the implementation......(and in this case I suppose I really can't use the interface.....)
thanks.

Answer 1

mickey0 wrote:
I read around that is normal thing write Set<String> set = new HashSet<String>() in place of HashSet<String> set = new HasSet<String>();Just to add to George's good advice, the basic reason is that if you decide later on that your Set is better off as a TreeSet instead of a HashSet, you can simply change the assignement to
Set<String> set = new TreeSet<String>();indeed, since all your methods will likely be coded to take Sets if you used the above method, you could probably change it to
NavigableSet<String> set = new TreeSet<String>();without any problems.
Moreover, If I got something right, the interface "could" not have "few" method of the implementation......(and in this case I suppose I really can't use the interface.....)The only method that HashSet has that Set doesn't is 'clone()'. Obviously, when choosing the interface, it should be as close as possible to to the capabilities you need.
Winston