Calling a function from the value of a string Java [duplicate]

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

**I have looked at this : Call a function from a string array (Java or Groovy) and it didn't work for me, perhaps it is my scenario*

I have a String array with some values, and I want to be able to call a method which is one of those values, of course this can change, and I could potentially have 100's of values, so it's not feasible to use a if/else if construct, or a switch statement.

Is there any way I can call the method, as I would like, as displayed in the code below?

private String[] = {"Hit","Slap","Blop"}; private String et = "Slap"; public void Action(){ for(int i = 0; i < arr.length;i++){ if(et.equals(arr[i])){ //Call method of that name ( Slap(); ) } } } public void Run(){ /// } public void Slap(){ /// } public void Blop(){ /// }

EDIT: My attempt to integrate reflection:

 for(int i = 0; i < arr.length;i++){ if(et.equals(arr[i])){ //Call method of that name try { method = this.getClass().getMethod(arr[i]); } catch (NoSuchMethodException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SecurityException e) { // TODO Auto-generated catch block e.printStackTrace(); } try { return (String) method.invoke(this); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } return "FAIL";

What did you try with reflection? It would be helpful to actually tell us what you tired rather than just stating it doesn't work when clearly reflection would work. — Jon Taylor
– Jon Taylor, Commented Jan 20, 2013 at 20:48
If you're calling the method identified by et, why bother looking it up in the array? — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Jan 20, 2013 at 20:49
The accepted answer in the first comment would work. In your case, you can change where they use "obj" to "this" since your methods are in the current class. — Erik Nedwidek
– Erik Nedwidek, Commented Jan 20, 2013 at 20:50
you can not call the method-object if it is null. it does not return any value, so do not cast and return the result. put your getMethod and the invoke in one try block instead... — Martin Seeler
– Martin Seeler, Commented Jan 20, 2013 at 21:01

partlov · Accepted Answer · 2013-01-20 20:50:41Z

2

You will have to use reflection. Something like this:

getClass().getMethod(arr[i]).invoke(this);

answered Jan 20, 2013 at 20:50

partlov

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1 Comment

JEV Over a year ago

--Working with this aswell. All the same.

Martin Seeler · Accepted Answer · 2013-01-20 21:09:25Z

You can use the ReflectionAPI to achieve this. Just get the method with this name from your desired class (if available ) and invoke it with your args, in this case null.

BUT it's a bad design and you should rethink your application flow!

here is an example:

public class HelloWorld { public static void main(String[] args) { HelloWorld hello = new HelloWorld(); String[] calls = { "def", "abc", "ghi" }; try { for (String call : calls) { Method method = HelloWorld.class.getMethod(call, null); method.invoke(hello, null); } } catch (Exception e) { // TODO: handle exception } } public void abc() { System.out.println("abc"); } public void def() { System.out.println("def"); } public void ghi() { System.out.println("ghi"); }

}

What do you consider a bad design? Using the Reflection api?

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