In the development of complex software systems, interactions between different program features increase the design complexity. Feature-oriented software development focuses on the representation and compositions of features. The implementation of features often cuts across object-oriented module boundaries and hence comprises interactions. The manual detection and treatment of feature interactions requires a deep knowledge of the implementation details of the features involved. Our goal is to detect interactions automatically using specifications by means of design by contract and automated theorem proving. We provide a software tool that operates on programs in Java and the Java Modeling Language (JML). We discuss which kinds of feature interactions can be detected automatically with our tool and how to detect other kinds of interactions.