If you have Java 7, I would definitely go with
Path source = ...
Path target = ...
Files.copy(source, target)
With the java.nio.file.Path class, it can work with symbolic and hard links. From java.nio.file.Files:
This class consists exclusively of static methods that operate on
files, directories, or other types of files. In most cases, the
methods defined here will delegate to the associated file system
provider to perform the file operations.
Just as references:
Copy files from one folder to another with Groovy
http://groovyconsole.appspot.com/view.groovy?id=8001
My second option would be the ant task with AntBuilder.