what are collections code example

Example 1: what type of collections used

Depending on the data that I am working with, I use
Arrays, Lists, Sets, Maps.

Example 2: collections

LIST: Can store duplicate values,Keeps the insertion order.
- ArrayList not syncronized, array based class 
- LinkedList not synchronized, doubly linked
- Vector is synchronized, thread safe
SET: Can only store unique values,And does not maintain order
- HashSet can have null, order is not guaranteed
- LinkedHashSet can have null and keeps the order 
- TreeSet sorts the order and don't accept null 
QUQUE :Accepts duplicates, Doesn't have index num,
First in first our order.        
MAP:is a (key-value format) 
and keys are always unique, 
and value can be duplicated. 
- HashTable don't have null key, sychronized(thread-safe)
- LinkedHashMap can have null key, keeps order
- HasHMap can have null key, order is not guaranteed
- TreeMap doesn't have null key and keys are sorted
Examples
 ■ I have used TreeSet to print dropdown list in for 
 non duplicate values and ascending order 
■ I have used HashMaps to compare values from 
a database with expected values