Difference between spring setter and interface injection?

I know how constructor and setter injection works in spring.

Interfaces on an abstract class

My coworker and I have different opinions on the relationship between base classes and interfaces. I’m of the belief that a class should not implement an interface unless that class can be used when an implementation of the interface is required. In other words, I like to see code like this:

Should interfaces extend (and in doing so inherit methods of) other interfaces

Although this is a general question it is also specific to a problem I am currently experiencing. I currently have an interface specified in my solution called

Declaring interface in the same file as the base class, is it a good practice?

To be interchangable and testable, normally services with logic needs to have interface, e.g.

Function that requires many parameters

I have a problem related to this:

Should concrete classes avoid calling other concrete classes, except for data objects?

In Appendix A to The Art of Unit Testing, Roy Osherove, speaking about ways to write testable code from the start, says,

Java – What methods to put in an interface and what to keep out

I’m designing a file handler interface:

Why to say, my function is of IFly type rather than saying it’s Airplane type

Say, I have two classes:

Two interfaces with identical signatures

I am attempting to model a card game where cards have two important sets of features:

Instantiating Interfaces in C#?

I am reading/learning about interfaces in C# at the moment, and thus far I managed to understand how it differs from an abstract class. In the book I am reading the author explains that interfaces are the ultimate abstract class and that it simply sets the standard of certain methods the inheriting class will have, but then provides the following example.