Call a function from a string array (Java or Groovy)

Question

In Java, or Groovy, say I have a String array like

myArray = ["SA1", "SA2", "SA3", "SA4"]

I want to call a different function based off of each string.

class Myclass{
  public static void SA1() {
    //doMyStuff
  }
  public static void SA2() {
    //doMyStuff
  }
  ...etc
}

I would love to be able to loop through my array and call the functions that they pertain to without having to compare the string or make a case statement. For example is there a way to do something like the following, I know it doesn't currently work:

Myclass[myArray[0]]();

Or if you have suggestions of another way I can structure something similar.

micha · Accepted Answer · 2012-12-24 16:06:41Z

4

In groovy you can do:

Myclass.(myArray[0])()

In Java you can do:

MyClass.class.getMethod(myArray[0]).invoke(null);

answered Dec 24, 2012 at 16:06

micha

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5 Comments

Kyle Weller Over a year ago

Hallelujah! I'm so glad I am using groovy. That's exactly what I was trying to do.

Kyle Weller Over a year ago

And on your java example, what is the null for when you invoke the method?

micha Over a year ago

Normally you want to execute methods on objects. In this case you have to pass the object you want to use. But in your example you are using static methods so no object is needed. Thats why null is passed to the invoke method.

Will Over a year ago

@micha, why println Myclass.(myArray[0])() works but myArray.each { println Myclass.(it)() } doesn't?

micha Over a year ago

Hm good question, I am not sure. MyClass.(it.toString())() works

Will · Accepted Answer · 2012-12-24 17:15:22Z

4

In Groovy, you can use a GString for dynamic method invocation:

myArray.each {
  println Myclass."$it"()
}

answered Dec 24, 2012 at 17:15

Will

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Comments

fge · Accepted Answer · 2012-12-24 16:01:41Z

2

You can, for instance, declare an interface such as:

public interface Processor
{
    void process(String arg);
}

then implement this interface, for example in singletons.

Then create a Map<String, Processor> where keys are your strings, values are implementations and, when invoking:

Processor p = theMap.containsKey(theString)
    ? theMap.get(theString)
    : defaultProcessor;

p.process(theString);

answered Dec 24, 2012 at 16:01

fge

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Comments

Ahmed M Farghali · Accepted Answer · 2013-06-06 13:12:37Z

0

I suggest you look at Reflection APIs, to call methods at runtime check Reflection docs

Class cl = Class.forName("/* your class */");
Object obj = cl.newInstance();

//call each method from the loop
Method method = cl.getDeclaredMethod("/* methodName */", params);
method.invoke(obj, null);

edited Jun 6, 2013 at 13:12

answered Dec 24, 2012 at 16:03

Ahmed M Farghali

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