How do you override a method for a java type instance with Groovy meta programming?

Question

I am trying to override the functionality of a method of a java type instance in my Groovy code but I am getting a classcast exception.

I looked at the guide posted her

Answer 1

Have you looked at Pimp my Library Pattern which allows you to add using Groovy Categories. You might find it more convenient and easy to understand in your case.

@Category(String)
class StringSubstrCategory {      
    def substring( int n)   { 
        "This is not a very good substring implementation"
    }
}

use (StringSubstrCategory) {
    "hey".substring(1)
}