container:
Collection Interface: defines a way to access a set of objects, and which sub-interface Set List define the storage
List: storing data in an orderly and repeatable ----> ArrayList
Set: Data storage disorder and can not be repeated ----> HashSet
Collection way of example: container class object call remove, whether the comparison target contains equal when other methods, using the object type equals and hashCode methods
For custom type, you need to be rewritten to implement equals and hashCode method custom rule objects are equal
Note: Equal objects should have equal hash codes
Generic: current type which can store only the data sets
Iterator: iterator used to traverse the collection