Naming convention for interface / class / mockClass in Java?

Question

I'm creating a mock class for a Lexer object, and I think I may need to do some refactoring. I have two options:

1. Create an interface Lexer, and rename the current Lexer to something like RealLexer. Have MockLexer implement Lexer, and method calls take anything of type Lexer. I dislike that my precious Lexer class is now renamed to something that has no meaning if you don't know that there's a mock class.
2. Create an interface LexerInterface (which I already dislike, since it has Interface in its name), but allowing myself to keep the current Lexer the way it is. MockLexer then implements LexerInterface. Another downside is that method calls take LexerInterface as params.

Both options smell bad to me, so I figured I'd let standards decide for me. Has anyone had experience with this?

Answer 1

I'd definitely vote for using Lexer as your interface name. How about adding some information about how or why your implementation does its thing as part of the name? E.g.:

• StringParsingLexer
• TokenizingLexer
• SingleThreadedLexer
• {ThirdPartyLibraryName}DelegatingLexer

Also, do you really need to be explicitly constructing a MockLexer? Using a framework like Mockito can make your testing considerably easier and faster; You can get started as easily as:

Lexer mockLexer = Mockito.mock(Lexer.class);

Mockito.when(mockLexer.doFoo()).thenReturn("bar");

Answer 2

My recommendation, as I stated in the comments, is to use Lexer for your interface and DefaultLexer for the default implementation. This pattern is used quite frequently and as such is very understandable to anyone who will be maintaining your code. As for the mock object, it would also be understandable to name this something like MockLexer.

As an example of a naming convention that Java uses:

javax.swing.table.TableModel is an interface
javax.swing.table.AbstractTableModel is an abstract class implementing TableModel
javax.swing.table.DefaultTableModel is an implementation of AbstractTableModel.

There is however, no recommendation in the Java Codding Conventions outside of using capital letters, nouns, etc.