Type names without static type checking already improve the usability of APIs (as long as the type names are correct): an empirical study

In the discussion about the usefulness of static or dynamic type systems there is often the statement that static type systems improve the documentation of software. In the meantime there exists even some empirical evidence for this statement. One of the possible explanations for this positive influence is that the static type system of programming languages such as Java require developers to write down the type names, i.e. lexical representations which potentially help developers. Because of that there is a plausible hypothesis that the main benefit comes from the type names and not from the static type checks that are based on these names. In order to argue for or against static type systems it is desirable to check this plausible hypothesis in an experimental way. This paper describes an experiment with 20 participants that has been performed in order to check whether developers using an unknown API already benefit (in terms of development time) from the pure syntactical representation of type names without static type checking. The result of the study is that developers do benefit from the type names in an API's source code. But already a single wrong type name has a measurable significant negative impact on the development time in comparison to APIs without type names.