How do I prevent the use of arbitrary methods, for example String.lastIndexOf()

Question

I have a scenario where I want to run code that I don't control. I want to prevent arbitrary standard JDK methods from being used in that code (for example, I want to prevent the usage of the lastIndexOf() method on any String objects).

If a forbidden method is used, it should result in a run time exception.

I suspect this might be possible with a custom class loader but I'm not sure how to approach this. Part of the problem I ran into is that String is a final class that can't be extended.

Example:

//I control this code
int result = SomeClass.method("foo") //I don't control SomeClass

//A valid implementation of SomeClass.method()
int method(String in) {return 1;}

//An invalid implementation of SomeClass.method()
int method(String in) {return in.lastIndexOf("o");}
//the above should throw an error at run time when called from my code

Answer 1

I suggested Reflection as a solution but what you want is an approach to tackle your problem and not a technical solution for it.

The domain of your problem can be much bigger than what we are discussing here.

Answer 2

I remember writing a custom findbugs detector that looked for specific method calls. In my case it analysed it's parameters as well, but it looks your case is a bit simpler.

Alternatively, you can use ASM library.

Most naively, you can disassemble the class with javap and grep the output.