Question

Example: If I have two classes: A and B. both class can call a method in C (example: the init() method)

From C, how do we know where the call is from (from Class A or Class B) ?

Answer 1

To do it right, you should provide C’s method with that information, for example via an enum or class parameter:

public void init(Object otherArg, Class<?> caller) {
    ...
}

or

public void init(Object otherArg, CallerEnum caller) {
    ...
}

But if you don’t care, there is another way using the stack trace. Have a look at Get current stack trace in Java and use the second StackTraceElement from the top of the stack to get the method that called the current one.