Using FileCallable from System Groovy or Script Console

[Brantone]

Has anyone been able to get the example from http://javadoc.jenkins-ci.org/hudson/FilePath.html to actually run in Script Console?

Direct copy-paste doesn't work, didn't work, complaints ex:

Script1.groovy: 10: The class 'Freshen' has an incorrect modifier static.
 @ line 10, column 2.
    private static final class Freshen implements FileCallable<Void> {

 ... other threads have pointed out using MasterToSlaveFileCallable , didn't work, errors of either unserializable or file not found (what file?)

I feel like I'm missing a crucial piece of info here, but all of the "oh just tweak this" recommendations are not useful for resolution. Perhaps permissions / creds issue?

Although a bit of slave-side computation is going on, it's nothing ridiculous, so just using FilePath is recommended method?

Thoughts?