How to check in Groovy that object is a list or collection or array?

Question

The question is as simple as the title. How to check in Groovy that object is a list or collection or array? But can\'t find a simple way of checking it. Any ideas?

Answer 1

If you are looking for a Groovy way, look at in operator. It is actually a combination of Class.isAssignableFrom(Class) and Class.isInstance(Object) meaning that you can use it to test classes as well as objects.

// Test classes
assert ArrayList in Collection
assert ArrayList in List
assert HashSet in Collection
assert HashSet in Set

// Test objects
def list = [] as ArrayList
def set = [] as HashSet

assert list in Collection
assert list in List
assert set in Collection
assert set in Set

Testing if an object is an array may be tricky. I would recommend @BurtBeckwith's approach.

def array = [].toArray()

assert array.getClass().isArray()