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Separate names with a comma.
The error is on line 99.
I'd recommend taking a look at this to see how I know this, it's an absolutely essential skill for writing Java.
If you look at the stack trace you're getting, you can see that you're getting a ClassCastException, this means that you're trying to convert a...
A different way to do this would be to use an iterator.
Example with the explanation for OP:...
The shade plugin is entered into your pom.xml, you configure it there too.
Get the original text, change it then set it back to the sign.
You would need to have the quotes around it, as it is a string. You would then manually parse it.
Alternatively you can use a String List which...
That is also part of the Spigot API