The document provides information on Java APIs, IO packages, streams, serialization, networking and TCP sockets. It defines that an API allows communication between programs, Java IO handles input/output through streams, and common IO classes include FileInputStream, FileOutputStream. Networking concepts covered include sockets, ports, IP addresses and protocols like TCP. TCP sockets in Java use Socket and ServerSocket classes.

1. CHAPTER 5
INPUT OUTPUT AND FILE
OPERATIONS

2. WHAT IS JAVAAPI???
• API stands for Application Programming Interface.
• It is a collection of communication protocols and subroutines used by
various programs to communicate between them.
• It plays a very important role while building software.
• An API helps two programs or applications to communicate with each
other by providing them with the necessary tools and functions.
• It takes the request from the user and sends it to the service provider
and then again sends the result generated from the service provider to
the desired user.

3. WHAT IS JAVAAPI???
• An API is similar to a GUI(Graphical User Interface) with one major
difference. Unlike GUIs, an API helps software developers to access
web tools while a GUI helps to make a program easier to understand
by users.
• The working of an API can be clearly explained with a few simple
steps. Think of a client-server architecture where the client sends the
request via a medium to the server and receives the response through
the same medium.
• An API acts as a communication medium between two programs or
systems for functioning.

4. JAVA IO API
• Java IO API helps the users to read and write data. In simple words,
we can say that the Java IO helps the users to take the input and
produce output based on that input.
• Java I/O (Input and Output) is used to process the input and produce
the output. Java uses the concept of a stream to make I/O operations
fast. The java.io package contains all the classes required for input and
output operations. We can perform file handling in Java by Java I/O
API.
• The Java IO API is placed in the java.io package. This package
comprises almost all classes that a user requires to perform input and
output (I/O) in Java. The java.io package generally involves reading
basic information from a source and writing it to a destination.

5. JAVA.IO PACKAGE
• The “java.io” package offers classes to read and write files, streams,
and other input/output devices. This package includes classes like
“InputStream,” “OutputStream,” “Reader,” and “Writer.”
• Java performs IO through Stream class.
• Some of the important classes in java.io package are as follows:
BufferedInputStream, BufferedOutputStream, BufferedReader,
BufferedWriter, ByteArrayInputStream, ByteArrayOutputStream,
FileIputStream, FileOutputStream, StringReader, StringWriter, etc.

6. STREAM CLASS
• A stream can be defined as a sequence of data.
• All these streams represent an input source and an output destination.
• The stream in the java.io package supports many data such as
primitives, object, localized characters, etc.
• The InputStream is used to read data from a source and the
OutputStream is used for writing data to a destination. InputStream
and OutputStream are the basic stream classes in Java.
• There are two types of stream classes:
Byte Stream Class
Character Stream Class

7. BYTE STREAM CLASS
• Byte Stream Classes are used to read bytes from an input stream and
write bytes to an output stream.
• There are many classes related to byte streams but the most frequently
used classes are, FileInputStream and FileOutputStream.
• FileInputStream class is used to read bytes from a file. It should be
used to read byte-oriented data for example to read image, audio,
video etc.
• FileOutputStream is an output stream for writing data to a file.
FileOutputStream will create the file before opening it for output. On
opening a read only file, it will throw an exception.

8. FileOutputStream Method
Method Meaning
Void write(byte[] b) This method writes b. length bytes from the
specified byte array to this file output stream
Void write(byte[] b, int off, int len) This method writes len bytes from the specified
byte array starting at offset off to this file output
stream
Void write(int b) This method writes the specified byte to this file
output stream
Void close() This method closes this file output stream and
releases any system resources associated with this
stream

9. FileInputStream Method
Method Meaning
Int available() an estimate of the number of remaining bytes that
can be read
Int read() It is used to read the byte of data from the input
stream
Int read(byte[] b) used to read up to b.length bytes of data from the
input stream.
Int read(byte[] b, int off, int len) It is used to read up to len bytes of data from the
input stream.
Long skip(long x) used to skip over and discards x bytes of data
from the input stream.
Void close() used to closes the stream.

10. BYTE STREAM CLASS
STREAM CLASS MEANING
FileInputStream Input stream that reads from a file
FileOutputStream Output stream that writes to a file
ByteArrayInputStream Input stream that reads from a byte array
ByteArrayOutputStream Output stream that writes to a byte array
InputStream Abstract class that describes stream input
OutputStream Abstract class that describes stream output
RandomAccessFile Supports random access file I/O
SequenceInputStream Input stream that is a combination of two or more
input streams that will be read sequentially, one
after the other
BufferedInputStream Buffered input stream
BufferedOutputStream Buffered output stream

11. CHARACTER STREAM CLASS
• Character streams in Java are designed for handling the input and
output of characters. They use 16-bit Unicode characters.
• Though there are many classes related to character streams but the
most frequently used classes are, FileReader and FileWriter.
• Though internally FileReader uses FileInputStream and FileWriter
uses FileOutputStream but here the major difference is that FileReader
reads two bytes at a time and FileWriter writes two bytes at a time.

12. CHARACTER STREAM CLASS
STREAM CLASS MEANING
BufferedReader Buffered input character stream
BufferedWriter Buffered output character stream
CharArrayReader Input stream that reads from a character array
CharArrayWriter Output stream that writes to a character array
FileReader Input stream that reads from a file
FileWriter Output stream that writes to a file
InputStreamReader Input stream that translates bytes to characters
OutputStreamWriter Output stream that translates characters to bytes
Reader Abstract class that describes character stream
input
Writer Abstract class that describes character stream
output

13. SERIALIZATION
• Serialization in Java is a mechanism of writing the state of an object into a
byte-stream, so that it can be stored on to a file, or memory, or a database
for future access. It is mainly used in Hibernate, RMI, JPA, EJB and JMS
technologies.
• The reverse operation of serialization is called deserialization where byte-
stream is converted into an object. The serialization and deserialization
process is platform-independent, it means you can serialize an object on one
platform and deserialize it on a different platform.
• For serializing the object, we call the writeObject() method
of ObjectOutputStream class, and for deserialization we call
the readObject() method of ObjectInputStream class.

14. SERIALIZATION
• Syntax for the writeObject() method:
public final void writeObject(Object o) throws IO Exception
• Syntax for the readObject() method:
public final Object readObject() throws IOException,
ClassNotFoundException

15. NETWORKING
• Sockets are at the foundation of modern networking because a socket
allows a single computer to serve many different clients at once, as
well as to serve many different types of information. This is
accomplished through the use of a port, which is a numbered socket on
a particular machine.
• A server process is said to “listen” to a port until a client connects to it.
A server is allowed to accept multiple clients connected to the same
port number, although each session is unique. To manage multiple
client connections, a server process must be multi threaded or have
some other means of multiplexing the simultaneous I/O.

16. NETWORKING
• Socket communication takes place via a protocol. Internet Protocol
(IP)is a low-level routing protocol that breaks data into small packets
and sends them to an address across a network, which does not
guarantee to deliver said packets to the destination.
• Transmission Control Protocol(TCP) is a higher-level protocol that
manages to robustly string together these packets, sorting and
retransmitting them as necessary to reliably transmit data.
• A third protocol, User Datagram Protocol (UDP), sits next to TCP and
can be used directly to support fast, connectionless, unreliable
transport of packets.

17. NETWORKING
• A key component of the Internet is the address. Every computer on the
Internet has one.
• An Internet address is a number that uniquely identifies each computer
on the Net.
• Originally, all Internet addresses consisted of 32-bit values, organized
as four 8-bit values. This address type was specified by IPv4 (Internet
Protocol, version 4).
• However, a new addressing scheme, called IPv6 (Internet Protocol,
version 6) has come into play. IPv6 uses a 128-bit value to represent
an address, organized into eight 16-bit chunks.

18. DOMAIN NAME SERVER
• Just as the four numbers of an IP address describe a network hierarchy
from left to right, the name of an Internet address, called its domain
name, describes a machine's location in a name space from right to
left.
• For example, www.yahoo.com is in the com domain (commercial
sites), it is called Yahoo (company name) and www is the name of the
specific computer. www corresponds to rightmost number in the
equivalent IP address.

19. PROXY SERVER
• A proxy server speaks the client side of a protocol to another server.
• This is often required when clients have certain restrictions on which
servers they can connect to.
• Thus a client would connect to a proxy server which did not have such
restrictions and the proxy server would in turn communicate for the
client.

20. CLIENT SERVER MODEL
• A client is an entity that relies on another entity to accomplish some
task. A server is an entity whose sole purpose is to serve clients by
providing them with some kind of well-defined services such as
searching a database or accepting mail messages.
• The interaction between client and server is just like the interaction
between a lamp and an electrical socket. The power grid of the house
is the server and the lamp is the power client.
• The server is a permanently available resource whereas the client is
free to unplug after it has been served.

21. NETWORKING CLASSES
• The classes contained in the java.net package are shown below:
• Authenticator, Inet6Address, ServerSocket, CacheRequest,
InetAddress, Socket, CacheResponse, InetSocketAddress,
SocketAddress, ContentHandler, SocketImpel, CookieHandler,
JarURLConnection, SocketPermission, CookieManager,
MulticastSocket, DatagramPacket, NetPermission, DatagramSocket,
NetworkInterface, PasswordAuthentication, URLCLassLoader,
URLConnection, etc.

22. InetAddress Class
• The InetAddress class is used to convert the Domain Name (or textual
Internet address) of an Internet address into an object which represents
the address.
• The InetAddress class doesn't have any constructors but it has three
factory methods that can be used to create instances of the InetAddress
class.
• Factory methods are merely a convention whereby static methods in a
class return an instance of that class.

23. InetAddress Class
• Three commonly used InetAddress factory methods are shown here:
• static InetAddress getLocalHost( ) throws UnknownHostException
• static InetAddress getByName(String hostName) throws
UnknownHostException
• static InetAddress[ ] getAllByName(String hostName) throws
UnknownHostException
• InetAddress also includes the factory method getByAddress( ), which
takes an IP address and returns an InetAddress object.

24. TCP/IP SOCKETS
• TCP/IP sockets are used to implement reliable, bidirectional, persistent, point to
point, stream based between two hosts on the Internet.
• A socket can be used to connect Java's Input/Output system to other programs that
may reside either on the local machine or any other machine on the Internet.
• In Java, TCP sockets are classified as: TCP Server Socket TCP Client Socket
• The java.net package provides two classes that allow you to create the two kinds
of sockets. The classes are Socket and ServerSocket respectively.
• The Socket class, basically used to create client sockets, is designed to connect to
server sockets and initiate protocol exchanges.
• The ServerSocket class, basically used to create server sockets, is designed to be a
listener, which waits for clients to connect before doing anything.
• When you create a Socket object, it implicitly establishes the connection between
the client and the server.

25. TCP/IP SOCKETS
• The socket class provides some constructors to create client sockets.
Constructor Name Description
Socket(string hostname, int port)
throws UnknownHostException,
IOException
This constructor is used to create a
client socket and connect the local
host to the specified hostName and
port. It can throw an
UnknownHostException or an
IOException.
Socket (InetAddress ipAddress, int
port) throws IOException
This constructor is used to create a
client socket using a pre existing
InetAddress object and a port. It can
throw an IOException.

26. TCP/IP SOCKETS
• After you have created a socket, you can get the address and port
details associated with the socket by the use of the following methods:
Method Name Description
InetAddress getInetAddress() Returns the address associated with
the socket instance.
Int getPort() Returns the remote port to which this
socket is connected.
Int getLocalPort() Returns the local port to which this
socket instance is connected.

27. WRITING SERVER PROGRAM USING TCP
Step-1: Create the server socket and begin listening.
Step-2: Call the accept( ) method to get new connections.
Step-3: Create input and output streams for the returned socket.
Step-4: Conduct the conversation based on the agreed protocol.
Step-5: Close the Client Stream and the Socket
Step-6: Go back to step 2 or continue to step 7
Step-7: Close the Server Socket.

28. WRITING CLIENT PROGRAM USING TCP
• Step-1: Create the client socket connection.
• Step-2: Acquire read and write streams for the socket.
• Step-3: Use the streams according to the server’s protocol.
• Step-4: Close the stream.
• Step-5: Close the socket