FileReader in a BufferedReader

FileReader in a BufferedReader

e.g.,

​new BufferedReader(new FileReader(...))

The primary purpose of wrapping a FileReader in a BufferedReader is to significantly improve I/O performance by adding an internal buffer, reducing slow, direct disk accesses; it reads large chunks of data into memory at once, making operations like readLine() much faster and more efficient for text files. Essentially, FileReader handles file access, while BufferedReader efficiently manages the reading of that data in larger, more manageable blocks, preventing repeated, costly system calls for single characters or small reads.

Key Benefits

• Performance Boost: Avoids frequent disk reads by fetching data in large chunks, drastically speeding up reading, especially for large files.
• Convenient Methods: Adds useful methods like readLine() (for reading entire lines) and lines() (for streams of lines), which aren't available in FileReader.
• Abstraction: BufferedReader wraps any Reader (like FileReader), providing a consistent, efficient way to handle various character streams.

Analogy

• FileReader → Reads characters from a file (basic character stream).
• BufferedReader → Wraps another Reader to add buffering, which reduces disk I/O calls and provides convenient methods like readLine().

Typical Use Cases

​1. Reading a Text File Line-by-Line

Efficient for processing large files without loading them entirely into memory.

import java.io.*; 
 
public class ReadFileExample { 
    public static void main(String[] args) { 
        String filePath = "data.txt"; 
 
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))) { 
            String line; 
            while ((line = br.readLine()) != null) { 
                System.out.println(line); // Process each line 
            } 
        } catch (IOException e) { 
            System.err.println("Error reading file: " + e.getMessage()); 
        } 
    } 
} 

Why BufferedReader?
readLine() is only available in BufferedReader, not FileReader.

2. Parsing Structured Text Files (CSV, Logs, Configs)

​import java.io.*; 
 
public class CSVReader { 
    public static void main(String[] args) { 
        String filePath = "data.csv"; 
 
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))) { 
            String line; 
            while ((line = br.readLine()) != null) { 
                String[] columns = line.split(","); 
                System.out.printf("Name: %s, Age: %s%n", columns[0], columns[1]); 
            } 
        } catch (IOException e) { 
            e.printStackTrace(); 
        } 
    } 
} 

Why?
BufferedReader reads chunks into memory, reducing the number of disk reads.

4. Filtering or Searching in a File

​import java.io.*; 
 
public class SearchInFile { 
    public static void main(String[] args) { 
        String filePath = "application.log"; 
        String keyword = "ERROR"; 
 
        try (BufferedReader br = new BufferedReader(new FileReader(filePath))) { 
            String line; 
            while ((line = br.readLine()) != null) { 
                if (line.contains(keyword)) { 
                    System.out.println(line); 
                } 
            } 
        } catch (IOException e) { 
            e.printStackTrace(); 
        } 
    } 
} 

Use case: Log scanning, keyword search.

Best Practices

​

• Always use try-with-resources to auto-close streams.
• Specify character encoding explicitly with InputStreamReader if not using the platform default:

new BufferedReader(new InputStreamReader(new FileInputStream("file.txt"), StandardCharsets.UTF_8)) 

• Adjust buffer size for very large files if needed.
• Avoid reading the whole file into memory unless necessary.