Puzzler: Capitalized file name matching Class name

[tamouse]

In class "Intro to Groovy", I saved my Person class from the console to the file Person.groovy. When I ran:

$ groovy Person.groovy

it threw the following exception:

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
/Users/tamara/Projects/groovy-stuff/Person.groovy: 1: Invalid duplicate class definition of class Person : The source /Users/tamara/Projects/groovy-stuff/Person.groovy contains at least two definitions of the class Person.
One of the classes is an explicit generated class using the class statement, the other is a class generated from the script body based on the file name. Solutions are to change the file name or to change the class name.
 @ line 1, column 1.
   class Person {
   ^

1 error

A bit of a puzzler. The "fix" is to make the filename not match the class name.

$ mv Person.groovy person.groovy
Person.groovy -> person.groovy

tamara@pontiki2:~/Projects/groovy-stuff:2016-06-18@11:27:02
$ groovy person.groovy 
[class:class Person, first:big, company:null, last:deal]
[class:class Person, first:big, company:yolo, last:deal]
big deal at yolo

This is the code:

class Person {
String first
String last
String company

String toString() {
  "$first $last at $company".toString()
}

}

Person me = new Person(first: "big", last: "deal")
println me.properties
me.company = "yolo"
println me.properties
println me.toString()