Java Input/Output Quiz

Redirecting System.out to a File

• To redirect System.out, use the System.setOut() method with a PrintStream object.
• Create a FileOutputStream for the file you want to write to.
• Create a PrintStream using the FileOutputStream object.
• Pass the PrintStream object to the System.setOut() method.
• Any output to System.out will now be written to the file.
• Use a try-catch block to handle potential FileNotFoundException.

Key Methods of the InputStream Class

• read(): Reads a single byte from the input stream.
• read(byte[] data): Reads multiple bytes into a byte array.
• read(byte[] data, int off, int len): Reads bytes into a byte array, starting from a specific offset and for a specified length.
• skip(long n): Skips over a specified number of bytes without reading them.
• available(): Returns the number of bytes ready to be read without blocking.
• close(): Closes the input stream, releasing resources.

BufferedInputStream Functionality

• BufferedInputStream enhances efficiency by buffering data, reducing the number of read operations from the underlying input stream.
• This is helpful when reading from slow sources like files or network sockets.

Reading Data from System.in

• The standard input stream (System.in) is typically associated with the keyboard.
• You can read data from System.in using the InputStreamReader class.
• InputStreamReader converts bytes from the input stream to characters.

BufferedReader and BufferedWriter Classes

• BufferedReader: Provides buffered reading, improving reading efficiency from slow sources.
• readLine(): Reads a line of text from the input stream.
• BufferedWriter: Provides buffered writing, improving writing efficiency for large amounts of data.

PrintWriter vs. PrintStream

• PrintWriter is the recommended class for formatted text output.
• Both classes offer similar methods for formatted printing.
• PrintWriter is character-based and has better character encoding support than PrintStream.

Reading and Writing to Text Files

• Create a FileOutputStream or FileInputStream to access the file.
• Create a PrintWriter (for writing) or a BufferedReader (for reading) using the stream.
• Use the appropriate methods to write to the file (e.g., println()) or to read from the file (e.g., readLine())
• Close the streams to release resources.

Sockets in Network Programming

• Sockets are endpoints of a communication link between two processes on a network.
• Two main types of sockets used in TCP communication:
  • ServerSocket (server-side): Listens for incoming connection requests.
  • Socket (client-side): Initiates a connection to a server.

Sockets Handling Multiple Client Requests

• ServerSocket listens on a specific port for client requests.
• When a client connects, accept() method creates a new Socket for that client.
• Each client connection has its own dedicated socket, enabling concurrent communication with multiple clients.

The InetAddress Class

• Represents an IP address (IPv4 or IPv6) and a domain name (hostname).

getByName() and getLocalHost() Methods

• getByName(String host): Resolves a hostname to an IP address and returns an InetAddress object.
• getLocalHost(): Returns the InetAddress object for the local machine.

InetAddress Getter Methods

• getHostName(): Returns the hostname as a string.
• getCanonicalHostName(): Returns the fully qualified domain name.
• getAddress(): Returns the network address as a byte array.
• getHostAddress(): Returns the IP address in dotted-quad format.

ServerSocket Constructors

• ServerSocket(int port): Creates a ServerSocket on a specific port.
• ServerSocket(int port, int queueLength): Creates a ServerSocket with a specified backlog queue length.
• ServerSocket(int port, int queueLength, InetAddress bindAddress): Creates a ServerSocket bound to a specific address and port.
• ServerSocket(): Creates an unbound ServerSocket.

Creating a TCP Server Socket

1. Create a ServerSocket object.
2. Listen for a client to connect using accept().
3. Create a new Socket from the accepted connection.
4. Obtain input and output streams from the Socket.
5. Handle communication with the client.
6. Close the Socket after communication is finished.

The Socket Class For TCP Clients

• Represents the client-side socket in a TCP connection.
• Used to initiate a connection to a server.

Creating a TCP Client Socket

1. Create a Socket object, passing the server's hostname and port.
2. Obtain input and output streams from the Socket.
3. Communicate with the server using the streams.
4. Close the Socket when communication is complete.

Obtaining Information About Sockets

ServerSocket Methods:

• getInetAddress(): Returns the local host address to which the server socket is bound.
• getLocalPort(): Returns the local port number to which the server socket is bound.

Socket Methods:

• getInetAddress(): Returns the remote host address to which the client socket is connected.
• getPort(): Returns the remote port number to which the client socket is connected.
• getLocalAddress(): Returns the local address to which the client socket is bound.
• getLocalPort(): Returns the local port number to which the client socket is bound.

URLs and URIs

• URL (Uniform Resource Locator): Specifies the location of a resource and a mechanism for retrieving it (e.g., a web address).

• URI (Uniform Resource Identifier): A broader term identifying a resource. It may not necessarily provide location or access instructions.

• All URLs are URIs, but not all URIs are URLs.

• A URI might be a name, while a URL gives the complete address and access method