Groovy by feature - Making Java Groovy - page 413

Map keys
When adding to a map, the keys are assumed to be of type string , so no quotes are ne-
cessary.
You can add to a map using either Java or Groovy syntax:
def ALEast [ 10 ] = [:]
ALEast.put('Boston','Red Sox')
assert 'Red Sox' == ALEast.get('Boston')
assert ALEast == [Boston:'Red Sox']
ALEast['New York'] = 'Yankees'
10 For non-baseball people, ALEast is short for the Eastern division of the American League.
Accessing values can be done with either the array-like syntax shown, or using a dot. If the
key has spaces in it, wrap the key in quotes:
assert 'Red Sox' == ALEast.Boston
assert 'Yankees' == ALEast.'New York'
I've been using def to define the map reference, but Groovy understands Java generics:
Map<String,String> ALCentral = [Cleveland:'Indians',
Chicago:'White Sox',Detroit:'Tigers']
assert 3 == ALCentral.size()
assert ALCentral.Cleveland == 'Indians'
Maps have a size method that returns the number of entries. Actually, the size method
is universal.
Size
In Groovy, the size method works for arrays, lists, maps, strings, and more.
Maps have an overloaded plus operation that combines the entries from two maps: