**Course Title:** Comprehensive Java Programming: From Basics to Advanced Concepts **Section Title:** File I/O and Working with External Data **Topic:** Write a program that reads data from a file, processes it, and writes the output to another file. (Lab topic) ### Objective In this lab topic, you will learn how to write a Java program that reads data from a file, processes it, and writes the output to another file. This program will demonstrate your understanding of file input/output (I/O) operations in Java. ### Pre-requisites Before starting this topic, make sure you have a good understanding of the following concepts: 1. Java's File I/O operations (reading and writing files) 2. Working with data formats (text, CSV, and JSON) 3. Handling file exceptions and using try-with-resources ### Problem Statement Suppose you are given a text file called `input.txt` that contains a list of names and ages, one per line, separated by a comma. Your task is to write a Java program that reads this file, converts the ages to uppercase, and writes the output to another file called `output.txt`. ### Step-by-Step Solution #### Step 1: Create a Java project and set up the input and output files Create a new Java project in your IDE (e.g., IntelliJ or Eclipse) and create two text files: `input.txt` and `output.txt`. Place the following data in `input.txt`: ``` John,25 Alice,30 Bob,35 ``` #### Step 2: Write the Java program to read data from the input file Create a new Java class called `FileProcessor` and add the following code: ```java import java.io.*; public class FileProcessor { public static void main(String[] args) { try (BufferedReader reader = new BufferedReader(new FileReader("input.txt"))) { String line; while ((line = reader.readLine()) != null) { // Process each line of data String[] parts = line.split(","); String name = parts[0]; String age = parts[1].toUpperCase(); System.out.println("Name: " + name + ", Age: " + age); // Write the processed data to the output file try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt", true))) { writer.write(name + "," + age + "\n"); } } } catch (IOException e) { System.err.println("Error reading input file: " + e.getMessage()); } } } ``` #### Step 3: Run the program and verify the output Run the `FileProcessor` class and verify that the data has been correctly processed and written to the `output.txt` file. ### Example Use Cases This program demonstrates a real-world scenario where data needs to be read from a file, processed, and written to another file. Some other examples of this scenario include: * Data migration: Reading data from an old system and writing it to a new system. * Data transformation: Reading data from a file, converting it to a different format, and writing it to another file. * Report generation: Reading data from a database or file and writing it to a report file. ### Best Practices When working with file I/O operations in Java, keep the following best practices in mind: * Always use try-with-resources to ensure that file resources are properly closed. * Use `BufferedReader` and `BufferedWriter` to improve performance. * Use `FileReader` and `FileWriter` to read and write text files. * Always handle exceptions and errors properly. ### Conclusion In this lab topic, you learned how to write a Java program that reads data from a file, processes it, and writes the output to another file. This program demonstrates your understanding of file I/O operations in Java and provides a foundation for more complex file processing tasks. ### Additional Resources For more information on Java's File I/O operations, see the following resources: * [Java API Documentation: java.io package](https://docs.oracle.com/javase/8/docs/api/java/io/package-summary.html) * [Java API Documentation: java.nio package](https://docs.oracle.com/javase/8/docs/api/java/nio/package-summary.html) ### Leave a Comment or Ask for Help If you have any questions or need help with this topic, please leave a comment below.