Map

Map allows key to value mapping for arbitrary value types, and many key types.

Created Map object has methods:

set(key, value)	Maps key to value. If key already has a mapping, the previous value disappears. If key is nil, the result is unspecified.	key - map key value - map key value
exists(key)	Returns true if key has a mapping, false otherwise. If key is nil, the result is unspecified.	key - map key
remove(key)	Removes the mapping of key and returns true if such a mapping existed, false otherwise. If key is nil, the result is unspecified.	key - map key
keys()	Returns an Iterator over the keys of this Map. The order of keys is undefined.
iterator()	Returns an Iterator over the values of this Map. The order of values is undefined.
toString()	Returns a String representation of this Map. The exact representation depends on the platform and key-type.