Clever Geek Handbook

How do I refer to method objects in Java?

Or, in other words, what's 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 methods, I just want to use them as objects! What to do?

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3 answers


It works, I can't help but wonder what are you doing about it?



new Method[] { 
  Vector.class.getMethod("add", Object.class), 
  Vector.class.getMethod("remove", Object.class) 
};
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First of all, you compose the syntax here. There is no "Vector.add ()" in my javadocs.

You can do it:




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

but you cannot follow these methods. There are no closures or function objects here.

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It works:)

I use this to instantiate a variable number of "folded" loops (loop within loop in loop).

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

EDIT: Rough code - it took me 3 minutes to write, so there is probably something very bad hiding there, but the general idea is obvious I guess.

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 all of this for, I'm just doing a permutation where the number of items is less than the number of positions. I ran into problems trying to define a variable number of loops (which depends on the number of positions), so I decided to work around it with this.

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