Add a dynamic "commify" to Groovy's ArrayList

BootStrap.groovy

class BootStrap {
    def init = { servletContext ->
        ArrayList.metaClass.commify = {
            StringBuilder output = new StringBuilder()

            for (int i = 0; i < delegate.size(); i++) {
                if (i == 0) {
                    output.append(delegate[i])
                } else if (i == delegate.size() - 1) {
                    output.append(" and ${delegate[i]}")
                } else {
                    output.append(", ${delegate[i]}")
                }
            }

            return output.toString()
        }
    }

    def destroy = {
    }
}