Calì is a quick and dirty implementation of a call log instrumentator based on javassist that modifies existing classes adds a print statement reporting the (fully qualified) method name and actual parameters of selected methods of a given class.
Assuming that the fat jar of this tool is build/libs/cali-0.1.0.jar and that your classes have been compiled in build/classes/java/test, the invocation
java -cp build/libs/cali-0.1.2.jar:build/classes/java/main it.unimi.di.prog2.cali.Cali it.unimi.di.prog2.example.Example twice
produces the output
Instrumented method it.unimi.di.prog2.example.Example.twice(int)
Instrumented method it.unimi.di.prog2.example.Example.twice(double)
meaning that all the methods called twice of the Example class have been instrumented; the modified code is written in build/classes/java/instrumented so that the following invocation
java -cp build/classes/java/instrumented it.unimi.di.prog2.example.Example
produces the output
it.unimi.di.prog2.example.Example.twice(3)
6
it.unimi.di.prog2.example.Example.twice(1.5)
3.0
in which odd lines are the call logging inserted by cali.