What is the difference between the HashMap and Map objects in Java?

Question

What is the difference between the following maps I create (in another question, people answered using them seemingly interchangeably and I\'m wondering if/how they are diff

Answer 1

You create the same maps.

But you can fill the difference when you will use it. With first case you'll be able to use special HashMap methods (but I don't remember anyone realy useful), and you'll be able to pass it as a HashMap parameter:

public void foo (HashMap m1 = ...;
Map m2 = ...;

foo (m1);
foo ((HashMap)m2);