Groovy ExpandoMetaClass lets you add instance methods, static methods, constructors, and operators to any class at runtime. 10+ tested examples included. “ExpandoMetaClass is Groovy’s answer to open classes. If you wish a Java class had a method, just add it.” Guillaume Laforge, Groovy Project Lead Last Updated: March 2026 | Tested on: Groovy 5.x, Java 17+ | Difficulty: Intermediate to Advanced | Reading Time: 18 minutes Ever wished String had a method to check for palindromes, or that Integer could ... Read More