Reading Text Files in Java with FileReader and BufferedReader

Every modern application depends on input and output (I/O) to process data — from text editors reading documents, to databases parsing logs, to cloud-based services synchronizing configuration files. In Java, two of the most commonly used classes for reading text files are FileReader and BufferedReader.

While FileReader provides a straightforward way to read characters from a file, BufferedReader enhances performance by buffering input, reducing costly disk access operations. Together, they form the backbone of text file handling in Java applications.

Basics of Java I/O

Streams, Readers, and Writers

Java I/O revolves around streams and readers/writers:

Streams (InputStream, OutputStream): Handle binary data.
Readers (Reader, FileReader): Handle character data.
Writers (Writer, FileWriter): Write character data.

For text files, we prefer Reader/Writer classes.

Example: Using FileReader

import java.io.FileReader;
import java.io.IOException;

public class FileReaderExample {
    public static void main(String[] args) {
        try (FileReader fr = new FileReader("example.txt")) {
            int character;
            while ((character = fr.read()) != -1) {
                System.out.print((char) character);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Example: Using BufferedReader

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class BufferedReaderExample {
    public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("example.txt"))) {
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Analogy: Reading with BufferedReader is like pouring tea into a cup before sipping, rather than drinking directly from the kettle one drop at a time.

Intermediate Concepts

Buffered I/O and Efficiency

BufferedReader stores chunks of data in memory, reducing direct file access. This is critical for large text files.

RandomAccessFile

For scenarios requiring random access to text (e.g., skipping to a line number), RandomAccessFile can complement FileReader.

Serialization & Deserialization

Though text reading is separate from serialization, configuration often involves mixing object serialization with text-based metadata.

Reading CSV, JSON, and XML

CSV: Wrap FileReader inside BufferedReader for parsing lines.
JSON/XML: Libraries like Jackson, Gson, or DOM/SAX parse streams provided by FileReader.

Properties Files

The Properties class can load .properties files using a FileReader.

Advanced I/O with NIO and NIO.2

Path and Files API

Modern Java prefers Path and Files API:

import java.nio.file.*;

public class FilesExample {
    public static void main(String[] args) throws Exception {
        Files.lines(Paths.get("example.txt")).forEach(System.out::println);
    }
}

Channels and Buffers

NIO provides FileChannel and ByteBuffer for high-performance file handling.

WatchService

Monitor directories for file changes — useful when reading continuously updated logs.

File Locking

Prevent concurrent write/read conflicts with file locking mechanisms.

Performance & Best Practices

Always use try-with-resources to close readers automatically.
Use BufferedReader for large text files.

Specify character encoding explicitly when necessary:

new InputStreamReader(new FileInputStream("file.txt"), "UTF-8")

Validate file paths to avoid security risks.
For very large files, consider streaming APIs or NIO.2.

Framework Case Studies

Spring Boot: Reading configuration files on startup using BufferedReader.
Logging Frameworks: Log4j/SimpleLogger parse configs using FileReader.
Netty: Uses NIO under the hood but can integrate with text file configs.
Hibernate: Reads hibernate.cfg.xml and persistence.xml using resource streams.
Microservices: Read YAML/JSON configuration files into memory on startup.

Real-World Scenarios

Log Analyzer: Use BufferedReader to process massive log files.
Import Utility: Read CSV → insert into a database.
Export Utility: Export database → JSON using Writers.
REST API: Stream large text files efficiently.
Compressed Files: Wrap streams inside GZIPInputStream for compressed log reading.

📌 What's New in Java Versions?

Java 7+: NIO.2 (Path, Files, WatchService).
Java 8: Stream API integration (Files.lines()).
Java 11: Files.readString(), Files.writeString().
Java 17: Performance improvements in NIO text processing.
Java 21: Virtual threads enabling scalable blocking I/O.

Conclusion & Key Takeaways

The FileReader and BufferedReader classes are fundamental tools for reading text files in Java. While FileReader offers simplicity, BufferedReader adds efficiency for larger files. Combined with modern APIs like NIO.2, they allow developers to handle file input cleanly, securely, and efficiently.

Key Takeaways:

Use FileReader for simple cases, BufferedReader for efficiency.
Prefer try-with-resources to handle closures.
Leverage NIO.2 for scalable solutions.
Always handle encoding and security properly.

FAQ

Q1. What’s the difference between FileReader and BufferedReader?
A: FileReader reads characters directly; BufferedReader buffers input for efficiency and can read entire lines.

Q2. Can I specify encoding with FileReader?
A: No, use InputStreamReader with explicit charset instead.

Q3. Is BufferedReader thread-safe?
A: No, external synchronization is needed in multi-threaded contexts.

Q4. How do I handle very large text files?
A: Use BufferedReader, streaming APIs, or Files.lines() with caution.

Q5. What’s better: BufferedReader or Scanner?
A: BufferedReader is faster for raw text reading; Scanner is better for tokenizing input.

Q6. How do I skip lines while reading with BufferedReader?
A: Simply call readLine() repeatedly until the desired line.

Q7. Can I reset FileReader to the beginning?
A: No, reopen the file or use RandomAccessFile.

Q8. How does NIO improve text file reading?
A: Provides channels, buffers, and streaming APIs for faster, scalable file handling.

Q9. Can I read compressed files with BufferedReader?
A: Yes, by wrapping streams in GZIPInputStream or ZipInputStream.

Q10. What’s the safest way to read configuration files?
A: Always validate file paths, handle exceptions, and specify encodings.