I work with smalltalk and java/eclipse so what I say come from this background. With statically typed languages and a IDE to aid, refactorings like rename, pull up, pull down, extract interface and such can be done without changing the code behaviour (if your code don't use reflection).This is a characteristic of statically typed languages, not IDEs, but IDEs can do it automatically. You could do this refactorings without a IDE, but not with text replace. For example, if you need to change the name of a method, category(), and two unrelated classes implements it, your refactor using text replace will change the method signature for both classes. You need to check every place where the code will be changed, and if your codebase is too big with too many calls, this is nearly impossible. The IDE rename the method calls based on the varible type, without risks of errors, if the refactoring is not possible eclipse warns you.