Function Calls from Main

Question

I have function A, function B, and function C

I am trying to call one of these function randomly (A or B or C) from Main.

How can i go about doing it?

Can i put the functions in an arraylist called FunctionList

Then do the following?

int x = (int)(Math.random() * Functionlist.size());
FunctionCall = FunctionList.get(x)

Possible duplicate - http://stackoverflow.com/questions/2752192/array-of-function-pointers-in-java — pyrospade, Aug 01 '12 at 23:29
What do you mean by function? Is it some method like `functionA()` or maybe some [strategy](http://en.wikipedia.org/wiki/Strategy_pattern) class `FunctionA`? — Pshemo, Aug 01 '12 at 23:31
I think he was hoping you could treat a funtion/method as an object, like you can do in other languages. — jahroy, Aug 01 '12 at 23:35
Another option would be to use reflection, though the comment above is likely a better approach. — jahroy, Aug 01 '12 at 23:36

score 2 · Accepted Answer · answered Aug 01 '12 at 23:26

2

If the number of functions is small, the easiest way would be a switch,

switch((int)(Math.random()*NUM_FUNCTIONS) {
    case 0:
        functionA();
        break;
    case 1:
        functionB();
        break;
  //  ...
}

answered Aug 01 '12 at 23:26

Daniel Fischer

174,737
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score 0 · Answer 2 · edited May 23 '17 at 12:13

Java doesn't support function pointers. One workaround would be to name your functions methodically, i.e. f1, f2, f3, etc... and then create a Method object based off of that pattern. For example, using the function names f1, f2, f3, you could do this:

java.lang.reflect.Method method;
try {
  methodName = "f" + String.valueOf((int) Math.random()*NUM_FUNCTIONS);
  method = obj.getClass().getMethod(methodName, param1.class, param2.class, ..); 
} catch (SecurityException e) {
  // ...
} catch (NoSuchMethodException e) {
  // ...
}

Then call the function like so:

try {
  method.invoke(obj, arg1, arg2,...);
} catch (IllegalArgumentException e) {
} catch (IllegalAccessException e) {
} catch (InvocationTargetException e) {

*This answer is heavily borrowed from here.

score 0 · Answer 3 · answered Aug 02 '12 at 07:15

0

I'd mimic function objects the standard way by creating -maybe anonymous- classes implementing some interface Function<T> with a method call(T arg), or even Runnable, if there's no argument. Instances of those can be put into a collection

answered Aug 02 '12 at 07:15

Heiko Schmitz

240
1
4

Function Calls from Main

3 Answers3