Java Generics 1 — Assignment

🎯 Objective

Learn to implement and use Generics in Java to enhance type safety and flexibility in your code.

This project demonstrates:

• Generic classes and methods
• Bounded type parameters
• Generic interfaces and implementations
• Type wildcards (?, ? extends)
• Practical use of generics in real applications

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🧱 Project Structure

Generic1/
├─ src/
│  └─ main/
│     └─ java/
│        └─ genericsdemo/
│           ├─ Box.java
│           ├─ NumberBox.java
│           ├─ Processor.java
│           ├─ StringProcessor.java
│           ├─ Library.java
│           └─ Main.java
└─ README.md

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⚙️ How to Compile and Run

1️⃣ Compile

Open PowerShell or Command Prompt in the project folder and run:

javac -d out src\main\java\genericsdemo\*.java

2️⃣ Run

After successful compilation, run:

java -cp out genericsdemo.Main

If you are using VS Code, you can also click the ▶️ Run button on Main.java.

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📚 Part 1 — Understanding Generics

✅ Generic Class: Box<T>

A class that can hold any data type safely.

Box<Integer> intBox = new Box<>(42);
Box<String> strBox = new Box<>("Hello Generics");

✅ Generic Method

A method that works for any type:

public static <U> void printBox(Box<U> box)

✅ Bounded Type Parameters: NumberBox<T extends Number>

Only accepts numeric types:

NumberBox<Integer> n1 = new NumberBox<>(10);
NumberBox<Double> n2 = new NumberBox<>(3.14);

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⚙️ Part 2 — Advanced Usage of Generics

✅ Generic Interface: Processor<T>

Defines a single method process().

✅ Implementation: StringProcessor

Implements Processor<String> and reverses input strings:

Processor<String> processor = new StringProcessor();
System.out.println(processor.process("Generics are powerful!"));

✅ Type Wildcards: Box<? extends Number>

Allows methods to handle boxes of any subclass of Number:

NumberBox.printNumberBox(new NumberBox<>(5.5));

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💼 Part 3 — Practical Application

✅ Generic Class: Library<T>

A generic library that manages any type of items (Books, DVDs, etc.). Features:

• add() — Add an item
• removeByName() — Remove an item by its name
• findByName() — Search by name
• listAll() — Show all items

Example:

Library<Book> bookLibrary = new Library<>(book -> book.title);
bookLibrary.add(new Book("Clean Code", "Robert C. Martin"));

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🧪 Test Cases for Demonstration Video

🧩 Normal Test Cases

#	Test	Expected Output
1	Store and retrieve using Box<Integer>	Prints stored integer
2	Reverse string using StringProcessor	Displays reversed string
3	Add, find, and remove in Library<Book>	Correct item found and removed

⚠️ Edge Test Cases

#	Test	Expected Output
1	Empty Box<String>	Prints "Box holds: null"
2	StringProcessor.process(null)	Returns null safely
3	Remove non-existing item from Library<Dvd>	Returns false, no crash

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🧩 Extra Credit Opportunity

To earn up to +5% extra credit, you can:

• Add a simple text menu (CLI) for user interaction
• Implement a Swing or JavaFX GUI to manage Library items
• Add advanced generic use cases like sorting or filtering with streams

Be sure to submit a short document explaining your enhancements and why they’re substantial.

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📂 Submission Requirements

• ✅ Push your complete project to a public GitHub repository

• ✅ Include this README.md

• ✅ Submit a demo video showing:

  • The program running successfully
  • 3 normal + 3 edge test cases passing

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🏁 Example Output

intBox.get() = 42
stringBox.get() = Hello Generics
Box holds: 42
Box holds: Hello Generics
nbInt = Box{10}
nbDouble = Box{3.1415}
NumberBox holds (as double): 10.0
NumberBox holds (as double): 3.1415
Original: Generics are powerful!
Reversed: !lufrewop era scireneG
Books: [Book{Clean Code by Robert C. Martin}, Book{Effective Java by Joshua Bloch}]
Find 'Clean Code': Book{Clean Code by Robert C. Martin}
Remove 'Effective Java': true
Books after removal: [Book{Clean Code by Robert C. Martin}]

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🧑‍💻 Author

Elida Ribeiro North Seattle College — Application Development Program Date: November 3, 2025