Collection: is a data structure for holding elements.
Collection<T>: is the highest level of the java’s framework for collection.
-Two main interfaces that extend Collection<T> interface:
- Does not allow duplication
- Does not impose an order on the elements
2.List<T> interface: (Allow duplication)
- Allow duplication
- Impose an order on the elements
-Two Abstract classes used (for convenience) to implement Set<T> and List<T> interface:
-If you want a class that implement The Set<t> interface, use the class HashSet<T>
HashSet<T>: is the concrete class implements the Set interface.
It can be used as a base class if you want to implement the Set interface.
-It is implemented using a hash table.
-If you want a concrete class that implement The List<t> interface, use
either the class ArrayList<T> or Vector<T>
They can be used as a base class if you want to implement the Set interface using your own class.