1. Introduction

1.1 Goal of the Tutorial

In this tutorial, we aim to understand the use of BufferedReader and BufferedWriter classes in Java.

1.2 Learning Outcome

After this tutorial, you will be able to use BufferedReader for reading text from a character-input stream and BufferedWriter for writing text to a character-output stream.

1.3 Prerequisites

Basic understanding of Java programming and I/O Streams in Java is required.

2. Step-by-Step Guide

2.1 BufferedReader

BufferedReader is a class in Java that reads text from an input-stream (like a file) buffering characters so as to provide efficient reading of characters, arrays, and lines. The buffer size may be specified, but by default it's large enough for most purposes.

Example:

BufferedReader reader = new BufferedReader(new FileReader("input.txt"));

2.2 BufferedWriter

BufferedWriter is a class in Java that writes text to an output-stream (like a file) buffering characters so as to provide efficient writing of single characters, arrays, and strings.

Example:

BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"));

3. Code Examples

3.1 Example: Reading from a File

import java.io.*;

public class ReadFile {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
        String line = null;
        while((line = reader.readLine()) != null) {
            System.out.println(line);
        }
        reader.close();
    }
}

In this example, we read each line from a file named "input.txt" and print it on the console. The readLine() method returns null when the end of the file is reached.

3.2 Example: Writing to a File

import java.io.*;

public class WriteFile {
    public static void main(String[] args) throws IOException {
        BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"));
        writer.write("This is a test line.");
        writer.newLine();
        writer.write("This is another test line.");
        writer.close();
    }
}

In this example, we write two lines into a file named "output.txt". The newLine() method is used to insert a newline.

4. Summary

In this tutorial, we have learned about reading from and writing to text files using BufferedReader and BufferedWriter in Java. We have seen how to iterate over each line in a file with BufferedReader and how to write lines to a file with BufferedWriter.

5. Practice Exercises

5.1 Exercise 1: Read a File and Count the Number of Lines

Write a Java program that reads a text file and prints the number of lines in the file.

5.2 Exercise 2: Copy Contents of One File to Another

Write a Java program that reads a text file and writes the contents into a new file.

5.3 Solutions

5.3.1 Solution to Exercise 1:

import java.io.*;

public class LineCount {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
        int lines = 0;
        while (reader.readLine() != null) lines++;
        reader.close();
        System.out.println("Number of lines: " + lines);
    }
}

5.3.2 Solution to Exercise 2:

import java.io.*;

public class FileCopy {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new FileReader("input.txt"));
        BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"));
        String line = null;
        while((line = reader.readLine()) != null) {
            writer.write(line);
            writer.newLine();
        }
        reader.close();
        writer.close();
    }
}

End of tutorial. Happy Learning!