I/O Stream Classes

1. Byte Stream
2. Character Stream

Byte Streams Classes:

• InputStream (Abstract class)
• OutputStream (Abstract class)
• FileInputStream (Reads text from existing file)
• FileOutputStream (Create a file and write text to it)
• ByteArrayInputStream
• ByteArrayOutputStream
• FilteredInputStream
• FilterOutputStream
• BufferedInputStream
• BufferedOutputStream
• SequenceInputStream (allows to concatenate multiple InputStream)
• PrintStream (Used for formatting like "printf" in c)
• DataInputStream  (Read a sequence of bytes and convert them into values of a primitive type)
• DataOutputStream (Convert values of primitive type into a byte sequence and then write it to the                 underlying stream)
• RandomAccessFile 

Character Streams Classes: (unicode characters)

• Reader (Abstract classes)
• Writer (Abstract classes)
• FileReader (Reads text from existing file)
• FileWriter  (Create a file and write text to it)
• CharArrayReader
• CharArrayWriter
• BufferedReader
• BufferedWriter
• PushbackReader
• PrintWriter (If the argument is not a primitive type, the PrintWriter methods (print, println ,format) will call the object's toString( ) method)

Difference between Iterator and Listitrerator

 Iterator

• Iterator is used to traverse Set and List and also Map type of Objects.
• Iterator is used retrieve the elements from Collection Object in forward direction only.

Listiterator

• List Iterator can be used to traverse for List type Objects, but not for Set type of Objects.
• List Iterator, which allows you to traverse in two directions.
• So it has another methods hasPrevious() & previous() other than Iterator.

Difference between ArrayList and Vector

ArrayList 

• It cannot be synchronized

Vector

• It can be synchronized

Map Interface

• Map
• Map.Entry
• NavigableMap
• SortedMap

Map Classes

Map - Have a key and value

• HashMap
• LinkedHashMap
• TreeMap

Collection Classes

Important Collection classes:
List - Duplicate objects can be loaded

• ArrayList implements List
• LinkedList implements List,Queue,Deque

Set - Duplicate objects cannot be loaded

• HashSet implements Set - (It does not guarantee the order of its elements)
• LinkedHashSet - (It ensures the order in which it is inserted)
• TreeSet implements NavigableSet - (Objects are stored in sorted, ascending order)
• PriorityQueue
• ArrayDeque - (It can be used as a stack)

Note:
peek() - return and removed

poll() - return but does not removed

Collection framework Interfaces

Collection framework interfaces are:

• Collection
• List (Duplicate Objects can be loaded)
• Queue
• Dequeue
• Set (No Duplicate objects)
• SortedSet (Objects are sorted)
• Navigable Set