Java BufferedReader Class — How to Read File in Java with Example

Overview

The BufferedReader class in Java is used for reading text from a character-input stream efficiently. It provides buffering capabilities, making it faster and more efficient when reading data from a file compared to reading character by character. In this documentation, we will explore how to use the BufferedReader class to read files in Java with a practical example.

Table of Contents

1. Introduction to BufferedReader Class
2. Creating a BufferedReader Object
3. Reading a File using BufferedReader
4. Closing the BufferedReader
5. Example: Reading a File using BufferedReader

1. Introduction to BufferedReader Class

The BufferedReader class is part of the java.io package and extends the Reader class. It provides efficient buffering of characters, which means it reads a chunk of characters from the underlying stream at a time, reducing the number of system calls and improving performance. This is particularly useful when reading large files.

2. Creating a BufferedReader Object

To use the BufferedReader class, we need to create a BufferedReader object associated with a Reader object. In the case of reading a file, we use the FileReader class, which is a subclass of Reader. Here's how you can create a BufferedReader object:

java
import java.io.*;

public class Main {
    public static void main(String[] args) {
        try {
            FileReader fileReader = new FileReader("example.txt");
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            
            // Now, you can use the bufferedReader object to read data from the file.
            
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. Reading a File using BufferedReader

Once you have created the BufferedReader object, you can use its various methods to read data from the file. The most commonly used method is readLine(), which reads a line of text from the file and returns it as a string. The reading process continues until the end of the file is reached, and null is returned. Here's how to read a file line by line:

java
import java.io.*;

public class Main {
    public static void main(String[] args) {
        try {
            FileReader fileReader = new FileReader("example.txt");
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                // Process the line of text here
                System.out.println(line);
            }
            
            bufferedReader.close(); // Don't forget to close the BufferedReader after use.
            
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

4. Closing the BufferedReader

It's essential to close the BufferedReader after using it to release system resources and avoid memory leaks. Closing the BufferedReader also ensures that any buffered data is properly flushed to the underlying stream. Failing to close the BufferedReader can result in unexpected behavior and resource contention.

5. Example: Reading a File using BufferedReader

Let's consider a simple example where we read and display the contents of a text file named "example.txt":

java
import java.io.*;

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

In this example, the program reads each line from the "example.txt" file and prints it to the console.

Note: Remember to replace "example.txt" with the actual path to your target file.

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This concludes the documentation on using the BufferedReader class to read files in Java. The BufferedReader class is an efficient way to read data from a file, and it can handle large files with ease. Always remember to handle exceptions and close the resources properly to ensure a robust and reliable program.