Is it possible to mock a class for all object and methods in a process?

[sunhong...@gmail.com]

I want to know if it is possible to  mock a class for all object and methods in a process, for example, the application under test is A, it reads a specific file in method M, the filereader is not a parameter of M, and M is invoked in different activity, I want to control the file content, is it possible to mock the filereader and set it to the application A, so any access to filereader is mocked.