What is Groovy's MetaClass used for?

Question

What is the use of Meta-Class in Groovy and other OO programming languages?

Answer 1

from Wikipedia

In object-oriented programming, a metaclass is a class whose instances are classes. Just as an ordinary class defines the behavior of certain objects, a metaclass defines the behavior of certain classes and their instances. Not all object-oriented programming languages support metaclasses. Among those that do, the extent to which metaclasses can override any given aspect of class behavior varies. Each language has its own metaobject protocol, a set of rules that govern how objects, classes, and metaclasses interact.

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Support in languages and tools

The following are some of the most prominent programming languages that support metaclasses. Common Lisp, via CLOS Groovy Objective-C Python Perl, via the metaclass pragma, as well as Moose Ruby Smalltalk Some less widespread languages that support metaclasses include OpenJava, OpenC++, OpenAda, CorbaScript, ObjVLisp, Object-Z, MODEL-K, XOTcl, and MELDC.