Creating a csv file from xml using groovy

Following up on the last article where I backed up the bank cds, I wanted to be able to query all of the cds at once to see if a check had cleared. In order to accomplish this, I mounted one of the backed up iso files, explored and found that most of the months used an xml file to list the cleared checks. I pulled the xml file from each iso into a directory and then used the following groovy code to read the file. Why groovy?, I guess it was the flavor of the day

This accomplished reading the file but then I wanted to output to a csv file. I decided to use the opencsv java package. After adding the import to the groovy script for import au.com.bytecode.opencsv.*, I then wrote the following code

Unfortunately the script did not run as opencsv expects a Listof String[] and did not like the groovy lists that it was given. Here's the exception:
Caught: java.lang.ClassCastException: [Ljava.util.ArrayList; cannot be cast to java.util.List at CheckClearer$_run_closure2.doCall(CheckClearer.groovy:30) at CheckClearer.run(CheckClearer.groovy:30)
I explicitly had to create String[]s and then pass them to CSVWriter. Here's the final script: