I/O Classes and Interfaces

Java’s I/O (Input/Output) system is robust and flexible, allowing programs to interact with various sources and destinations of data, including the console, files, and networks.

• The core I/O classes are found in the java.io package.

What is a Stream?

In Java, a stream is a continuous flow of data from a source to a destination.

There are two main types of streams:

• Input Streams: Read data from a source.
• Output Streams: Write data to a destination.

1.) Byte Streams: Handle raw bytes (e.g., images, audio, binary files).

• InputStream (abstract base class for byte input)
• OutputStream (abstract base class for byte output)
• Common concrete classes: FileInputStream, FileOutputStream, BufferedInputStream, BufferedOutputStream, DataInputStream, DataOutputStream.

2.) Character Streams: Handle characters (text data), which are more convenient for human-readable data as they handle character encodings.

• Reader (abstract base class for character input)
• Writer (abstract base class for character output)
• Common concrete classes: FileReader, FileWriter, BufferedReader, BufferedWriter, PrintWriter.

Common Interfaces:

• Closeable: Marks a resource that can be closed (e.g., streams). Used with try-with-resources.

• Flushable: Marks a destination that can be flushed (e.g., Writer to ensure data is written to the underlying device).

• Serializable: Used for object serialization (converting an object’s state into a byte stream for storage or transmission).

Example (Console I/O):

import java.util.Scanner;

public class ConsoleInput {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in); // System.in is an InputStream
        System.out.print("Enter your name: ");
        String name = scanner.nextLine();
        System.out.println("Hello, " + name + "!");
        scanner.close();
    }
}