example implementation of the visitor pattern in groovy

main.groovy

def randomElement
// simulate user input, for instance
if (new Random().nextInt() % 2 == 0) {
    randomElement = new Element1()
} else {
    randomElement = new Element2()
}

new PrinterVisitor().visit(randomElement)

visitor.groovy

package com.jakecoffman.visitor

interface IVisitor {
    void visit(Element1 e)
    void visit(Element2 e)
}

interface IElement {
    void accept(IVisitor visitor)
}

class Element1 implements IElement {
    String name
    String element1Specific

    Element1() {
        name = "Element1"
        element1Specific = "specific1"
    }

    @Override
    void accept(IVisitor visitor) {
        visitor.visit(this)
    }
}

class Element2 implements IElement {
    String name
    String element2Specific

    Element2() {
        name = "Element2"
        element2Specific = "specific2"
    }

    @Override
    void accept(IVisitor visitor) {
        visitor.visit(this)
    }
}

class PrinterVisitor implements IVisitor {
    @Override
    void visit(Element1 e) {
        println "${e.name} ${e.element1Specific}"
    }

    @Override
    void visit(Element2 e) {
        println "${e.name} ${e.element2Specific}"
    }
}