How do I use a map in Apex class?

You Can use Map in Apex following ways:

1. Creating a Map: Map<Key,Value> variablename=new Map<Key,Value>(); …
2. Different Methods in Map:
3. put(key, value): It returns the value with given key in the map. …
4. clear(): It removes all the key-value mapping pairs from the map.
5. get(key): …
6. keySet(): …
7. values(): …
8. size():