Hi All,

I'm having quite some trouble using array's in processing, i come from a ActionScript / Python background, and processing's implementation of array's is confusing me. I gather that i have to declare the length of my array up front, plus the datatype of the information inside the array. For some reason that's unclear to me i am not able then to "fill" the array with data so to speak.

code:
String[] fileNames = new String[numElements];

 for (int i = 0; i<numElements; i++) {
   XMLElement chart = xml.getChild(i);  
   String from = chart.getStringAttribute("from");
   String to = chart.getStringAttribute("to");
   String fileName = from + "-" + to + "-" + weeklyArtistChartListFilename + ".xml";
   fileNames = append(fileNames,fileName);
   
 }
 
 print(fileNames[0]);

now, the print statements keeps returning "null" to me for the total amount of elements that are in the array. So, where did the filenames go that i appended?

append() is nice if you don't know beforehand how many elements you need to put in the array, as it grows the array each time you need to add an element there.
It is nice for newbies which don't need to be submerged by concept of ArrayList to be converted to array later, for example.
But it is very costly, because on each append, a new array is created with one more element than the previous one, and the old array is copied there!

To make your code work with append, which adds always at the end of the array (ie. after the empty elements you created first!), you can use the following code instead:
Code:

int numElements = 10;
String[] fileNames = new String[0];
 
  for (int i = 0; i<numElements; i++) {
    String fileName = "Element " + i;
    fileNames = append(fileNames,fileName);
  }
   
  print(fileNames[0]);
 

(simplified for testing)
Otherwise, if you know in advance the final size of the array, do as polymonkey shown.

Yes. See ArrayList for a reference (but forget the generics notation, not supported by Processing yet).