HW-06-exceptions-and-file-handling/README.md

Sixth Assignment — Exceptions and Files

Introduction

In this assignment, you will practice working with:

• File reading and writing
• Exception handling
• CSV data processing
• Validation of user/file input
• Basic report generation

The goal is to build a small sales report system that reads product and order information from CSV files, validates the data, calculates totals, and generates a final report file.

This assignment focuses heavily on using exceptions and file operations correctly while keeping the program stable even when invalid data exists in the input files.

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Objectives

By completing this assignment, you should be able to:

• Read data from CSV files using Java file handling tools
• Parse and process text-based data
• Use exception handling (try-catch) to manage invalid input safely
• Validate numeric and logical data
• Skip invalid rows without stopping the entire program
• Generate and save reports into output files
• Organize code into multiple classes and methods
• Use Git and GitHub/Gitea workflows professionally

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Tasks

Part 1 — Load Product Data

Implement the loadProducts() method in Main.java.

Requirements:

• Read product data from products.csv
• Each line follows this format:

[productId],[name],[price]

Example:

1,Apple iPhone 16,999.99

Notes:

• The product file data is guaranteed to be valid.
• Every line contains exactly two commas.
• No additional validation is required for this file.

You should:

• Read each line
• Parse the values
• Create Product objects
• Store them inside productCatalog

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Part 2 — Process Order File

Implement the processFile() method in ReportGenerator.java.

The order details file follows this format:

[productId],[quantity],[discountPercent]

Example:

1,2,10
3,5,25

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Validation Rules

A line is considered invalid if:

• quantity is not a valid integer
• discountPercent is not a valid integer
• quantity <= 0
• discountPercent is outside the range 0–99
• The productId does not exist in productCatalog

If even one field is invalid, the entire line must be skipped.

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Important Requirement

You are strongly encouraged to use:

• try-catch
• exception handling
• NumberFormatException

to safely process invalid rows without terminating the program.

The program should continue processing the remaining lines even if some rows are invalid.

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Calculations

For every valid row:

subtotal = quantity × productPrice

discountValue = subtotal × discountPercent / 100

finalCost = subtotal - discountValue

Update the following totals:

• totalQuantity
• totalFinalCost
• totalDiscountValue
• totalInvalidLines

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Part 3 — Generate Report

Implement the saveReport() method.

The generated report should contain:

• Total quantity
• Total final cost
• Total discount value
• Number of invalid lines

Example:

===== SALES REPORT =====

Total Quantity: 25
Total Final Cost: 1520.50
Total Discount Value: 210.75
Invalid Lines: 3

Save the report into an output file.

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Submission ⌛

Before submitting:

• Add your mentor as a contributor to the repository
• Create a develop branch for implementation
• Use Git regularly with meaningful commits
• Push all code to the remote repository
• Push the answers/documentation file if required
• Create a Pull Request from develop → main

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Additional Resources 📚

Assignment Explanation Videos

• https://drive.meshcomp.ir/d/15b6b853da8d4ade97de/

Java File Handling

• https://docs.oracle.com/javase/tutorial/essential/io/

Java Exceptions

• https://docs.oracle.com/javase/tutorial/essential/exceptions/

Scanner Class

• https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html

Try-Catch in Java

• https://www.w3schools.com/java/java_try_catch.asp

Git Branching

• https://git-scm.com/book/en/v2/Git-Branching-Branches-in-a-Nutshell

CSV Basics

• https://en.wikipedia.org/wiki/Comma-separated_values