Background: When acquiring new programming languages, learners typically transfer their knowledge from previous languages to the new one. Recent studies demonstrate that this transfer is similar to the process of learning a second language, so learning can be more efficient, but also interference can take place, similar to false friends. While these studies demonstrate the existence of transfer, they have focused on programming languages with rather larger differences, such as Python versus Java.

Objective: Our goal is to understand how students transfer between two similar programming languages, that is, from C to Java, adding a different angle to how transfer takes place.

Method and Results: To this end, we gave students a Java comprehension test in the first week of a CS2 course, after they have completed a CS1 course based on C. We could confirm that students transfer knowledge from C to Java, including false friends. We repeated this study a year later, but included a dedicated Java tutorial before conducting the Java comprehension test. With these explicit instructions, students experienced less interference when learning Java, demonstrating that they profit from being made explicitly aware of syntactical intricacies of Java. However, we also observed persistent interference for some concepts, indicating the need for more in-depth instructions.