Java.Streams.What subclasses of the Reader class do you know, what are they for?

The Reader class is part of Java’s character-based I/O system, introduced to handle text data (as opposed to InputStream which handles raw bytes). Let’s go over the key subclasses and their purposes.

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📘 Reader Overview

• Reader is an abstract class in java.io for reading streams of characters.
• It is part of the character I/O hierarchy, introduced to work with Unicode text in a more natural way than byte streams.

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🔽 Common Subclasses of Reader

Subclass	Description
BufferedReader	Buffers characters for efficient reading, supports readLine().
InputStreamReader	Converts bytes from an InputStream into characters using a charset.
FileReader	A convenience subclass of InputStreamReader for reading from files (uses default charset).
CharArrayReader	Reads characters from a character array.
StringReader	Reads characters from a String.
PipedReader	Used with PipedWriter for inter-thread communication.
FilterReader	Abstract class for decorating Reader objects, base for custom filtering.
PushbackReader	Allows one character to be “pushed back” (unread), useful for parsers.

✅ Quick Examples

1. BufferedReader

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

2. InputStreamReader

InputStreamReader reader = new InputStreamReader(new FileInputStream("file.txt"), "UTF-8");
int ch;
while ((ch = reader.read()) != -1) {
    System.out.print((char) ch);
}
reader.close();

3. CharArrayReader

char[] chars = {'J', 'a', 'v', 'a'};
CharArrayReader reader = new CharArrayReader(chars);
int c;
while ((c = reader.read()) != -1) {
    System.out.print((char) c);
}
reader.close();

4. StringReader

StringReader reader = new StringReader("Hello Reader");
int ch;
while ((ch = reader.read()) != -1) {
    System.out.print((char) ch);
}
reader.close();

5. PushbackReader

PushbackReader reader = new PushbackReader(new StringReader("abc"));
int c = reader.read();
if (c != 'a') {
    reader.unread(c);
}
// Continue processing
reader.close();

🧵 Summary Table

Reader Subclass	Purpose
BufferedReader	Efficient reading, supports readLine()
InputStreamReader	Bridge from byte to character streams
FileReader	Reads characters from files
CharArrayReader	Reads from a character array
StringReader	Reads from a string
PipedReader	Inter-thread communication
FilterReader	Decorator base class
PushbackReader	Allows unread of characters (parser use)