Groovy closures can be invoked directly after we have defined them. This way we get the result immediately and can assign it to a variable. We use call() or () after we have defined the closure, so the closure code is executed and the return value of the closure is assigned to the variable.
def date = {
def d = new Date()
d.set year: 2010, month: Calendar.DECEMBER, date: 1
d.format "dd-MM-yyyy"
}()
assert date == '01-12-2010'
def text = {
def result = ''
"mrhaki".size().times {
result += it
}
result
}.call()
assert text == '012345'
