Groovy is awesome and closures are cool. In Java 8 we will see lambdas which are similar like closures. A Java lambda will be automatically converted to an interface type if the interface contains only one single abstract method (SAM). In Groovy we can convert a closure into an interface type by using the as keyword. But since Groovy 2.2 we don’t have to use the as keyword, but let Groovy, like Java lambdas, convert a closure implicitly to an interface type. This works for interfaces with a single method, but Groovy wouldn’t be Groovy if it didn’t work for abstract classes with one abstract method. So, yes, it also works for abstract classes with a single abstract method.