String foo() {
  // will be automatically converted to a String on account of the return type
  new StringBuilder('foo')
}

assert foo() == 'foo'

Set<Integer> foo() {
  // will be automatically converted to a Set on account of the return type
  [1, 2, 2]
}

assert foo().size() == 2

Integer foo(Object[] a) {
   a.length
}

List myList = [1, 2, 3]
assert 3 == foo(myList)

Integer foo(Object[] a) {
   a.length
}

List myList = [1, 2, 3]
assert 3 == foo(myList.toArray())

Integer foo(Integer[] l) {
  l.size()
}

assert 3 == foo([1, 2, 3])

Integer foo(Object[] l) {
  l.size()
}

def list = [1, 2, 3]
assert 3 == foo(*list)