Identification of potential refactoring opportunities is an important step in the refactoring process. In large systems, manual identification of useful refactoring opportunities requires a lot of effort and time; therefore, there is a need for automatic identification. However, this problem has not yet been addressed well for many non-trivial refactorings that highly improve code quality. Two such non-trivial, yet popular refactorings are “Replace Type Code with Subclass” (SC) and “Replace Type Code with State” (ST) refactorings. In this thesis,we present a formal definition of control-fields which forms the basis for the identification of SC/ST refactoring opportunities. We present novel static analyses to efficiently identify SC and ST refactoring opportunities.We have implemented our approach in a tool called Auto-SCST and evaluated its effectiveness on open-source Java applications.