You have a collision. Collisions between interface methods can always be resolved providing the following three conditions apply:
1: The methods have the same signature. (Otherwise it is overloading and not a collision at all).
2: The methods have compatible intent (see below).
3: The methods have the same return type. (You will have to check in the Java Language Specification for the exact details.)
You are violating no 3 here, and it will never compile.
This is overloadingAnd this is incompatible intentObviously the WackyArithmetic#add method is only suitable for jokes, but I challenge you to implement both those interfaces in accordance with their specifications given.
Have a look at these three add methods: note that the first is intentionally given a vague specification so both sub-interfaces can implement it differently, but still be compatible in intent. 123