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

Map is an interface that HashMap implements. The difference is that in the second implementation your reference to the HashMap will only allow the use of functions defined in the Map interface, while the first will allow the use of any public functions in HashMap (which includes the Map interface).

It will probably make more sense if you read Sun's interface tutorial