Mastering Java BufferedReader: Efficient Character Stream Handling

Java BufferedReader Class

Discover how the BufferedReader class boosts I/O performance in Java with practical examples and in‑depth method explanations.

The BufferedReader class, part of the java.io package, wraps another Reader to provide efficient character input. By reading chunks of data into an internal buffer, it minimizes expensive disk I/O operations.

How BufferedReader Works

Internally, BufferedReader maintains a buffer of 8,192 characters (default size). During a read operation, a block of characters is fetched from the source file and stored in this buffer. Subsequent reads then pull characters from the buffer one by one, drastically reducing the number of disk accesses and speeding up I/O.

Creating a BufferedReader

To use BufferedReader, import it from java.io and wrap any other Reader implementation, such as FileReader:

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

FileReader file = new FileReader("example.txt");
BufferedReader reader = new BufferedReader(file);

You can also specify a custom buffer size:

BufferedReader reader = new BufferedReader(file, 16384); // 16KB buffer

Key Methods of BufferedReader

read()

• int read() – reads a single character from the buffer.
• int read(char[] cbuf) – reads characters into the supplied array.
• int read(char[] cbuf, int off, int len) – reads up to len characters into the array starting at offset off.

Example: reading the entire content of input.txt into a character array:

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

class Main {
    public static void main(String[] args) {
        char[] buffer = new char[100];
        try (FileReader file = new FileReader("input.txt");
             BufferedReader reader = new BufferedReader(file)) {
            reader.read(buffer);
            System.out.println("Data in the file:\n" + new String(buffer));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Output

Data in the file:
This is a line of text inside the file.

skip()

The skip(long n) method discards the next n characters from the stream:

reader.skip(5); // skips "This "

After skipping, reading the remaining content yields:

Data after skipping 5 characters:
 is a line of text inside the file.

close()

Always close the reader to free system resources:

reader.close();

Other Useful Methods

For a complete reference, visit the official Java documentation.