My main question: I know you can generically output class fields with reflection, even if you do not know the variable names, types, or even how many there are. However, is there a way to list all variables within the current function or current scope, assuming I do not know what the variable names are?
In other words:
int x = 5;
int y = 42;
// some more code
//Now I want to println x and y, but assuming I cannot use "x" or "y".
I’d also be happy with an answer to this question:
Let’s say I’m allowed to store the names of all variables, does that help? e.g.:
Set<String> varNames = new HashSet<String>();
int x = 5;
varNames.add("x");
int y = 42;
varNames.add("y");
// some more code
//Now with varNames, can I output x and y without using "x" or "y"?
Why am I asking this? I am translating XYZ language(s) to java using ANTLR, and I would like to provide a simple method to output the entire state of the program at any point in time.
Third possible solution I’d be happy with: If this is not possible in Java, is there any way I can write byte-code for a function that visits the calling function and examines the stack? This would also solve the problem.
What would be amazing is if Java had the equivalent of Python’s eval() or php’s get_defined_vars().
If it makes a difference, I’m using Java 6, but anything for Java 5, 6, or 7 should be good.
Thanks!
You can’t, as far as I’m aware. At least, not with normal Java code. If you’re able to run the bytecode through some sort of post-processor before running it, and assuming you’re still building with the debug symbols included, then you could autogenerate the code to do it – but I don’t believe there’s any way of accessing local variables in the current stack frame via reflection.