input-output

Input-Output in Java

The goal of these programming exercises is to practise I/O concepts:

• Reading from a text file
• Writing to a text file

For the exercises below, we've provided the starter project above.

📌 File Input/Output

Part 1

Create a class called FileManager with the following methods:

• public List<String> readFile(String filename) - returns a List<String> object, where each list item is a line from the specified file
• public void copy(String inputFile, String outputFile) - copies the contents of a text file at the path defined by inputFile to the path defined by outputFile. Creates outputFile if it doesn't exist and overwrites it, if it does

🔖 Note:

The paths to inputFile and outputFile are relative to the root directory of this repository (e.g. exercises/input-output/src/main/resources/exercise.txt)

Part 2

Improve the FileManager class by using the java.nio.* classes to replace the logic of the readFile and copy methods.

Part 3

Add the following method to the FileManager class:

• public void reverseLines(String inputFile, String outputFile)
  • read the contents of inputFile
  • write the lines to outputFile, but in reverse order; the first line will be the last one, the second will be the penultimate, and so on, until the last line of the original file, which should appear in the first position of the resulting file.
  • create outputFile if it doesn't exist and overwrite it, if it does
  • look in this project's resources folder for both inputFile and outputFile
  • don't reuse any of the previous methods

✅ Verify Your Implementation

To verify that your code works as expected, run the provided unit tests.

In your terminal, ensure that you are in the input-output folder. Then run the following command in your terminal:

./mvnw clean test

If you are on Windows, run this command instead:

mvnw.cmd clean test

Tests Results

Your implementation is correct when all tests pass:

[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] ├─ App Test Suite - 0.018s
[INFO] │  └─ ✔ creates the app - 0.01s
[INFO] ├─ FileManager Test Suite - 0.035s
[INFO] │  ├─ ✔ copy() method copies file content to new file correctly - 0.009s
[INFO] │  ├─ ✔ copy() method overwrites existing file - 0.001s
[INFO] │  ├─ ✔ reverseLines() method copies empty content to new file correctly - 0.002s
[INFO] │  ├─ ✔ getReader() method throws IOException for non-existent file - 0.002s
[INFO] │  ├─ ✔ getReader() method can read file contents - 0.001s
[INFO] │  └─ ✔ reverseLines() method copies reversed content to new file correctly - 0.002s
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 7, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.192 s
[INFO] Finished at: 2023-09-07T15:27:50+01:00
[INFO] ------------------------------------------------------------------------

Stretch Goal

Once you've verified your class works correctly, you can utilise it in App.java.

Add the following methods and call them from the main method:

• public static void readFile(String filePath)
  • use a FileManager instance to read the contents of the sample file we've provided at resources/exercise.txt file
  • print the contents to the screen, line by line
• public static void reverseFile(String sourcePath, String targetPath)
  • use a FileManager instance to reverse the contents of the sample file we've provided at resources/exercise.txt file to a new file at resources/reversed.txt
  • read the contents of the reversed file
  • print the contents to the screen, line by line