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I have a String array that contains names of method in the yyyyyy class

In the xxxxxx class I'm making a yyyyyy instance (say obj). Now I can call obj.function_name(), except I want to read function_name from the String array in a loop. Is this possible?

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Can you elaborate ? Its not so clear to understand. – User 1034 Jun 16 '10 at 5:47
2  
I believe the term you're looking for is "reflection". – Stephen Jun 16 '10 at 5:47
and i'm also sure what he meant is this one: stackoverflow.com/questions/160970/… – gumuruh May 2 '12 at 7:54

4 Answers

up vote 10 down vote accepted

You can, using reflection. It is done by calling Yyyy.class.getMethod("methodName").invoke(someArgs)

You'd have to handle a bunch of exceptions, and your method must be public. Note that java coding conventions prefer methodName to method_name.

Using reflection, however, should be a last resort. You should be using more object-oriented techniques.

If you constantly need similar features, perhaps you can look at some dynamic language running on the java platform, like groovy

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up vote 6 down vote

It's possible using reflection, although you should probably question your design somewhat if you need that sort of behavior. Class.getMethod takes a String for the method name and returns a Method object, which you can then call .invoke on to call the method

I can't figure out the markdown to link these inline, but these Javadoc pages should be helpful:

Sample code (assuming the yyyyyy methods take one int argument, just to show argument passing):

yyyyyy obj = new yyyyyy();
String[] methodNames = {"foo", "bar", "baz"};
for(String methodName : methodNames) {
    Method method = Class.forName("yyyyyy").getMethod(methodName, new Class[] {int.class});
    method.invoke(obj, 4); // 4 is the argument to pass to the method
}
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Why don't you use obj.getClass() in stead of Class.forName("yyyyyy") ? – Marc Jun 16 '10 at 6:23
links are messed up, try replacing ( with %28 and ) with %29 – Sean Patrick Floyd Jun 16 '10 at 6:34
@Marc I actually prefer yyyyyy.class over either, but any work – Michael Mrozek Jun 16 '10 at 6:34
don't link to java 1.4.2 – Bozho Jun 16 '10 at 7:58
@Michael Mrozek the advantage of using obj.getClass() is that it always returns the correct type, even after refactoring the obj variable. – Marc Jun 16 '10 at 8:09
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up vote 0 down vote

Yes, using reflection and dynamic method invocation you can do this. If you google "java dynamic method invocation" you'll get some interesting hits.

Here is a tutorial. This implements a kind of plotting language like you are describing.

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