Untitled Quiz

Module III: Input/Output

• Java's I/O system (input/output) is supported by the java.io package, encompassing file I/O.
• Streams are used to facilitate I/O operations in Java, enabling faster processing. Streams represent a sequence of data.
• Java uses streams to manage input and output operations.
• The java.io package provides classes that support input and output operations.

The Stream Classes

• Java's stream-based I/O is grounded in four abstract classes:
  • InputStream: designed for byte streams.
  • OutputStream: designed for byte streams.
  • Reader: designed for character streams.
  • Writer: designed for character streams.
• Byte streams and character streams form separate hierarchies.
• Character streams are used for working with characters or strings.
• Byte streams are used for working with bytes or binary objects.

File and Directory Management

• The java.io package supplies the File class for file and directory management.
• File enables creating new files/folders, viewing properties, renaming, and deleting files/folders.
• import java.io.* is necessary to use File class.
• File class offers constructors for creating File objects from different inputs:
  • File(String directoryPath)
  • File(String directoryPath, String fileName)
  • File(File dirObj, String fileName)
  • File(URI uriObj)

Creating Files and Folders

• createNewFile() creates an empty file.
• mkdir() creates a directory.

Java FILE Class Methods

• canRead(): checks if a file is readable.
• canWrite(): checks if a file is writable.
• createNewFile(): creates a file.
• delete(): deletes a file.
• exists(): checks if a file/directory exists.
• getName(): returns the file's name.
• getAbsolutePath(): returns the absolute path.
• length(): returns file size in bytes.
• list(): returns an array of files within a directory.
• mkdir(): creates a directory.

Accessing File Properties (Methods)

• toString(): returns a string representation of the File.
• getName(): returns the file's or directory's name.
• getPath(): returns the path of the file.
• getAbsolutePath(): returns the absolute path.
• getParent(): returns the parent directory's path.
• exists(): checks if the file exists.
• canWrite(): checks if the file can be written to.
• canRead(): checks if the file can be read from.
• isDirectory(): checks if the given path is a directory.
• isFile(): checks if the given path is a file.
• isAbsolute(): checks if the path is absolute.
• isHidden(): checks if the file is hidden.

Renaming and Deleting Files

• renameTo(File newFile) renames the file.
• delete() deletes a file.
• deleteOnExit() schedules a file's deletion.

Types of Streams

• Byte Stream: Deals with input and output of bytes (8 bits). Used for binary data.
• Character Stream: Handles input and output of characters (16 bits). Efficient for text data.

Byte Stream Classes

• InputStream: Abstract base class for input byte streams.
• OutputStream: Abstract base class for output byte streams.
• FileInputStream: Reads from a file.
• FileOutputStream: Writes to a file.
• BufferedInputStream/BufferedOutputStream: Provide buffering for input/output.
• DataInputStream/DataOutputStream: For reading/writing primitive data types.

Character Stream Classes

• Reader: Abstract base class for character input.
• Writer: Abstract base class for character output.
• FileReader: Reads from a file.
• FileWriter: Writes to a file.
• BufferedReader/BufferedWriter: Provide buffering for character input/output.
• PrintWriter: Designed for formatted printing.

File Input/Output Stream Methods

• available(): Returns the estimated number of data bytes that are available in input stream.

• read(): Reads one byte from an input stream.

• read(byte[] b) reads bytes from stream to the array b.

• read(byte[] b, int off, int len) reads len bytes from offset off to b.

• skip(long n) skips over n bytes of input stream.

• close(): Closes the stream.

• write(byte[] b) writes bytes from b to an output stream.

• write(byte[] b, int off, int len) writes from bytes in b starting from offset off for len bytes.

• write(int b) writes a single byte b to the output stream.

• close(): Closes the output stream.

Reading/Writing Data from/to Files using Different Streams

• Methods for reading and writing data to files using various streams like FileInputStream, FileOutputStream, FileReader, FileWriter. Illustrates buffering techniques.

Reading Console Input

• Scanner: Converts byte stream to character stream, enabling convenient input of various datatypes (int, byte, long, short, float, double, boolean).
• BufferedReader: Used with InputStreamReader(System.in). Reads input from the command line.

Writing Console Output

• Methods for writing output to the console (print, println, write).
• PrintWriter is a recommended class for formatting output to the console.

Serialization

• Serialization is the process of converting the state of an object into a byte stream.
• writeObject() method ( ObjectOutputStream) serializes objects.
• readObject() method ( ObjectInputStream) deserializes objects.
• Serializable interface must be implemented for objects to be serializable.

Packages in Java

• Packages group similar classes for organization.
• Built-in packages provide core functionalities.
• package statement defines packages.
• import statement imports packages.

Access Protection

• Packages define access levels (public, protected, default, private).
• Access specifiers control code visibility and access.