Developing software from reusable libraries lets developers face a security dilemma: Either be efficient and reuse libraries as they are or inspect them, know about their resource usage, but possibly miss deadlines as reviews are a time consuming process. In this paper, we propose a novel capability inference mechanism for libraries written in Java. It uses a coarse-grained capability model for system resources that can be presented to developers. We found that the capability inference agrees by 86.81% on expectations towards capabilities that can be derived from project documentation. Moreover, our approach can find capabilities that cannot be discovered using project documentation. It is thus a helpful tool for developers mitigating the aforementioned dilemma.