Test how big it is with length or size


months = Hash.new
months.length
months.size # => 0

1.	Creating Hashes
2.	You can test to see if a hash is empty with empty?
3.	use new to create a hash with a default value which is otherwise just nil
4.	access any key in a hash that has a default value
5.	Hash with =>
6.	Hash.new with block logic
7.	This lazily initialized hash maps integers to their factorials

Test how big it is with length or size : Hash.new « Hash « Ruby