The answer to your question is yes, you can replace a class file, but it is somewhat complicated in that you have to be sure that no other dependencies have changed.
For example, if the class you are compiling involved changing method signatures of methods that are used in other classes, you will need to replace those as well. As long as the method signatures of public, protected, or default methods aren't changed, you should be okay.
As a side-note, if this is something you do often, you'll quickly realize why objects are often passed into methods instead of individual parameters.
public MyObject getObject(MyObject2 mySecondObject)
vs
public MyObject getObject(int a, int b, int c)
When you need to add a new property to an object passed into a method, the method signatures don't change, but when you add or remove a parameter on the method signature itself, it creates a chain reaction on all dependencies, requiring that you compile and replace those class files as well.
As a final point to highlight, it's worth noting that changes you make to private methods or private variables, or even the definitions of a method, have no bearing or impact on other class files. The only thing that matters is that you uphold the contract that your methods have with other classes in that the inputs and outputs always take and return the same data types.
This highlights the importance of encapsulation of instance variables and how those dependencies are hidden from other classes.
