"Not tired yet? Let's carry on, then. I'd like to give you more details about Set and Map and what they can do."

"Set is a set, a group of unnumbered objects. The main feature of a Set is that it only contains unique objects, i.e. each element of the set is different. Here are operations you can perform on a set:"

Operation Method
Add element(s) add(), addAll()
Remove element(s) remove(), removeAll()
Check for the presence of element(s) contains(), containsAll()

"And that's it?"

"Well, yes. You can also use the size() method to find out how many elements are in the set."

"What about Map?"

"Map is a set of pairs. It's like a Set, except it's a set of key-value pairs rather than unique elements. The only limitation is that each «key» must be unique. A Map can't contain two pairs with the same keys."

"Here's what we can do with Map:"

Operation Method
Get a set of all pairs entrySet()
Get a set of all keys keySet()
Get a set of all values values()
Add a pair put(key, value)
Get the value for the specified key get(key)
Check whether the specified key is present containsKey(key)
Check whether the specified value is present containsValue(value)
Check whether the Map is empty isEmpty()
Clear the Map clear()
Remove the value for the specified key remove(key)

"This is much more interesting than Set."

"Yes. Although Map isn't as popular as List, it is used in many tasks."