Call different methods by its parameter

Question

I got an application which should call different methods, based on the params' input. My idea until now is basically, that I create a Switch and call the methods separately by its case. Example:

switch (methodName)
{
    case "method1":
        method1();
        break;
    case "method2":
        method2();
        break;
    default:
        System.out.println(methodName + " is not a valid method!");
}

I was considering the option to invoke the method by its given string, as provided in this question:

How do I invoke a Java method when given the method name as a string?

But then I read from one of the answers, that it's not safe. What do you guys think?

Have a look at this (similar) question: http://stackoverflow.com/questions/4480334/how-to-call-a-method-stored-in-a-hashmap-java — aioobe, Nov 15 '12 at 13:54
thank you guys, I wasn't sure what I need to search for (therefore I was unable to find good results to my question). I guess, you could already close my question, thanks a lot :) — Pascal Weber, Nov 15 '12 at 14:01

score 1 · Accepted Answer · answered Nov 15 '12 at 14:03

1

If you need to go from a string to a method call, reflection may be your best option. There are no great safety issues involved, especially if you constrain the set of methods that are allowed to be called. Using a Map<String, Method> is one way to achieve it, with the benefit of improved performance since the main bottleneck is not reflective method invocation, but method lookup.

Without reflection you could achieve this with a Map<String, Callable>, where you implement Callable with an anonymous class instance for each method call. Quite a bit more boilerplate code, but "type safe".

answered Nov 15 '12 at 14:03

Marko Topolnik

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great! how should the MethodCall look like? `Main.class.getMethod(command).invoke(null)`? – Pascal Weber Nov 15 '12 at 14:12
If `command` is a static method, then that's it. Otherwise, instead of `null` use the instance on which you want to call the method. Don't trip on exception handling, though: `try { ...reflection... } catch (RuntimeException e) { throw e; } catch (Exception e) { throw new RuntimeException(e); }`. – Marko Topolnik Nov 15 '12 at 14:13
I am having trouble with that though.. but it points to the right direction. Marked it as best answer! – Pascal Weber Nov 15 '12 at 14:36

score 0 · Answer 2 · answered Nov 15 '12 at 14:10

0

You can achieve the same functionality as reflection by using the Command design pattern. It wraps action into objects, so they can be looked up and invoked using a common interface.

Read more here: http://en.wikipedia.org/wiki/Command_pattern

answered Nov 15 '12 at 14:10

Jakub Zaverka

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Call different methods by its parameter

2 Answers2

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