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

As noted by TJ Crowder and Adamski, one reference is to an interface, the other to a specific implementation of the interface. According to Joshua Block, you should always attempt to code to interfaces, to allow you to better handle changes to underlying implementation - i.e. if HashMap suddenly was not ideal for your solution and you needed to change the map implementation, you could still use the Map interface, and change the instantiation type.