Two type declarations for a single variable in Groovy? -

while reading tutorial on gradle plugins, cam across following code:

apply plugin: greetingplugin  greeting.message = 'hi gradle'  class greetingplugin implements plugin<project> {     void apply(project project) {         // add 'greeting' extension object         project.extensions.create("greeting", greetingpluginextension)         // add task uses configuration         project.task('hello') << {             println project.greeting.message         }     } }  class greetingpluginextension {     def string message = 'hello greetingplugin' } 

my understanding line def string message = 'hello greetingplugin' declaring 2 types (both generic def type , specific string type). removing either of types seems allow script continue execute.

is there reason why groovy allows 2 type declarations made single variable? if so, use cases language feature , serve specific purpose in situation?

the line

def string message = 'hello greetingplugin' 

is wrong. def waste of characters in situation doesn't anything

that line same as

string message = 'hello greetingplugin' 

see def , type section in page