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.

score 4 · Accepted Answer · answered Dec 24 '12 at 16:06

4

In groovy you can do:

Myclass.(myArray[0])()

In Java you can do:

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

answered Dec 24 '12 at 16:06

micha

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1

Hallelujah! I'm so glad I am using groovy. That's exactly what I was trying to do. – Kyle Weller Dec 24 '12 at 16:10
And on your java example, what is the null for when you invoke the method? – Kyle Weller Dec 24 '12 at 16:12
1

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. – micha Dec 24 '12 at 16:14
@micha, why `println Myclass.(myArray[0])()` works but `myArray.each { println Myclass.(it)() }` doesn't? – Will Dec 24 '12 at 17:10
1

Hm good question, I am not sure. `MyClass.(it.toString())()` works – micha Dec 24 '12 at 17:19

score 4 · Answer 2 · answered Dec 24 '12 at 17:15

4

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

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

answered Dec 24 '12 at 17:15

Will

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score 2 · Answer 3 · answered Dec 24 '12 at 16:01

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);

Ahmed M Farghali · Answer 4 · 2013-06-06T13:12:37.260

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 06 '13 at 13:12

answered Dec 24 '12 at 16:03

Ahmed M Farghali

319
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12

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

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