I understand your doubt regarding map and hash map.
Please check out my answer, I hope it will clear your doubts.
- It is the implementation of map interface.
- It can contain null values and keys.
- It doesn't maintain input order.
- It is an interface
- Map has two implementation
- Tree Map
- Hash Map
- Tree Map maintains the input order .
- It will not allow any null values.
- Duplicate keys are not allowed in the map