Can you name the main classes for working with threads in Java?

In Java, the following main classes are used for input-output streams:

• InputStream and OutputStream — basic abstract classes for reading and writing bytes.
• Reader and Writer — basic abstract classes for reading and writing characters (text).
• Concrete implementations:
  • FileInputStream / FileOutputStream — for working with files at the byte level.
  • FileReader / FileWriter — for working with files at the character level.
  • BufferedInputStream / BufferedOutputStream — buffered streams for performance enhancement.
  • BufferedReader / BufferedWriter — buffered character streams.
  • DataInputStream / DataOutputStream — for reading and writing primitive data types.
  • ObjectInputStream / ObjectOutputStream — for object serialization.

In Android, these classes are used similarly, as Android is based on Java. Buffering and wrappers are often used for convenience and efficiency.

Example of reading a file using BufferedReader:

BufferedReader reader = new BufferedReader(new FileReader("file.txt"));
String line;
while ((line = reader.readLine()) != null) {
    System.out.println(line);
}
reader.close();

Thus, the main classes for streams are InputStream/OutputStream and Reader/Writer with their numerous implementations.