How to refer to Method objects in Java?

Question

Or, in other words, what is wrong with something like -

new Method[] {Vector.add(), Vector.remove()}

Eclipse keeps telling me that I need arguments. But I obviously don't want to call the methods, I just want to use them as objects! What to do?

Answer 1

this works, I can't help but wondering, what you're doing with this?

new Method[] { 
  Vector.class.getMethod("add", Object.class), 
  Vector.class.getMethod("remove", Object.class) 
};

Answer 2

First of all, you're making up syntax here. There's no "Vector.add()" in my javadocs.

You can do this:

Method [] methods = Vector.class.getMethods();

but you can't execute those methods. No closures or function objects here.

Answer 3

That works :)

I'm using this to instantiate a variable number of "stacked" loops (loop within a loop within a loop).

There is a static method to which you pass the starting index, limit, Object to invoke the methods with, and finally an array of methods and an array of arguments.

EDIT: Rough code - took me 3 minutes to write, so there's probably something very bad lurking in there, but the general idea is obvious, I think.

public static void loop(int start, int lessThan, Object obj, Method[] methods, Object[] args) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
     lastLoop++;
     for(int i = start; i < lessThan; i++) {
      for(int j = 0; j < methods.length; j++) {
       methods[j].invoke(obj, args[j]);
      }
     }
    }

If you're wondering what I'm using this whole thing for - I'm just tinkering around with a way to do permutations where the number of elements is less than the number of positions. I've ran into problems trying to define a variable number of loops (which depends on the number of positions), so decided to circumvent it with this.