Question

I am getting this warning on Sonar:

Avoid using implementation types like ‘HashMap’; use the interface
instead

What does it mean?

The class in which i get this warning is as:

class A {
   private HashMap<String, String> map=new HashMap<String, String>();

   //getters and setters

}

Please, I want proper solution to avoid warning on Sonar.

Answer 1

You should always code to an interface. ie. in this case you should declare your field like this:

private Map<String, String> map= new HashMap<String, String>();

This way anything using the map variable will treat it as type Map rather than HashMap.

This allows you to swap out the underlying implementation of your map at a later date without having to change any code. You are no longer tied to HashMap

Read through this question: What does it mean to "program to an interface"?

Also I am not sure what you were doing casting to a Set there?