Groovy by feature - Making Java Groovy - page 411

One particularly interesting feature of collections is that they support type coercion using
the as operator. What does that mean? It's not terribly difficult to convert a Java list into a
set, because there's a constructor for that purpose. Converting a list into an array, however,
involves some awkward, counterintuitive code. Here's Groovy's take on the process:
def names = teams as String[]
assert names.class == String[]
def set = teams as Set
assert set.class == java.util.HashSet
That was easy. [ 9 ] A set in Groovy is just like a set in Java, meaning it doesn't contain du-
plicates and doesn't guarantee order.
9 I know I say that a lot, but with Groovy I think it a lot, too.
The as operator
Groovy uses the keyword as for many purposes. One of them is type coercion, which con-
verts an instance of one class into an instance of another.
One of the nicest features of Groovy collections is that they're searchable. Groovy adds
both find and findAll methods to collections. The find method takes a closure and
returns the first element that satisfies the closure:
assert 'New Hampshire' ==
['New Hampshire','New Jersey','New York'].find { it =~ / New / }
The findAll method returns all the elements that satisfy the closure. This example re-
turns all the cities that have the letter e in their name:
def withE = cities.findAll { city -> city =~ / e / }
assert withE == ['Seattle', 'New York', 'Cleveland']
Groovy also supplies the methods any and every , which also take closures:
assert cities.any { it.size() < 7 }
assert cities.every { it.size() < 10 }