Software Refactoring

Software changes inevitably in its life-cycle. It changes for some reasons, for example, to erase errors, to adjust the changes of the requirements and the contexts and so on. The changes of software bring the problems of software entropy. Refactoring or restructuring can improve the internal structure without altering the external behavior and prevent codes from decaying. To some extend, it can counter the problem of software entropy.This paper provides a systematic research in the field of the software refactoring including its theory, method and strategies. This paper also introduces the basic Refactoring Tools used in the refactoring procedure.Though the research and analysis on the QinShan Nuclear System, the paper introduces the Software Refactoring driven by the Software Quality Audits methods, the Software Refactoring driven by the"bad code smells". Furthermore, the paper introduces the advanced refactoring based on the Design Pattern, and explains the technique to separate the user interface codes and the high performance share strategies. In addition, the paper concludes the process of refactoring based on the pattern design.By comparing the old system and the refactoring system, the refactoring got obvious effects: improving the quality of code and solute the problem of difficulty to maintain and extend the system.