Java Collection

List - List of things.
1. ArrayList -> Growable array. Good for fast iteration but not for a lot of insertion and deletion.
2. Vector -> Same as ArrayList but its methods are synchronized for thread safety.
3. LinkedList -> Same as ArrayList. Good for fast insertion and deletion but not for iteration.

Set - Unique things
1. HashSet -> Collection with no duplicate objects and unpredictable iteration order.
2. LinkedHashSet -> Ordered version of HashSet, ordered in which they are inserted.
3. TreeSet -> Sorted Set by natural order using Red-Black tree structure.

Map - Things with unique ID
1. HashMap -> The simplest map class.
2. Hashtable -> Same as HashMap but its methods are synchronized for thread safety.
3. LinkedHashMap -> Ordered version of HashMap, ordered in which they are inserted.
4. TreeMap -> Sorted Map by natural order.

Queue - Things arranged by the order in which they are to be processed
1. PriorityQueue