Compute a Java function's signature

Question

Is there a way to compute a Java class's method's signature? A signature
like ([Ljava/lang/String;)V represents a function that takes a String[] as argument
and returns void.

What's the rule to compute the signature?

Answer 1

It's always a set of parentheses enclosing type signifiers for the arguments, one after the other with no commas or anything, followed by a type signifier for the return value after the closing paren. It's pretty straightforward.

There's a table of type signatures on this page:

Signature    Java Type Z    boolean B    byte C    char S    short I    int J    long F    float D    double V    void L fully-qualified-class ;    fully-qualified-class [ type   type[] 

Those last two mean that to name a class, you say, for example, Ljava/lang/Object;, and to name an array of (for example) int, you say [I, and an array of array of int is [[I.

If you wanted to literally compute the signature in Java code based on reflection, it'd be simple enough; just use the table above with rules for handling objects and arrays.

Answer 2

Just run javap -s <class-name> in the folder containing the .class files . It will tell you with 100% accuracy. No need to guess these things.