In this Master's Thesis Project, two Code Smells, four Anti-Patterns and four types of Design Principle violations have been examined. We developed a detection program called the Anti-Pattern Scanner. This scanner has been used in an empirical evaluation where five open-source Java projects have been examined and scanned for these `pattern' problems. The results are that the examined problems generally do occur in software systems. The problems are estimated to be inconvenient to software development, depending on the strength of their presence. Based on the Anti-Pattern Scanner and the results from this evaluation, suggestions for follow-up studies are offered.