GENERICS - USE CASES

 

1. Basic ArrayList Manipulation

Problem:
Create a program to manage a bookstore inventory using ArrayList<Book>. Each Book has a title (String) and price (double).

• Add 5 books

• Remove the cheapest book

• Print the remaining books sorted by price

2. HashMap for Employee Database

Problem:
Build an employee ID lookup system using HashMap<Integer, Employee>.

• Add employees with ID as key

• Allow searching by ID

• Print all employees in alphabetical order

3. HashSet for Social Media Tags

Problem:
Implement a unique hashtag tracker for posts using HashSet<String>.

• Add tags like "#Java", "#Programming"

• Prevent duplicates

• Show trending tags in alphabetical order

4. PriorityQueue for Airport Security

Problem:
Simulate an airport security line where:

• First-class passengers (priority=1) go first

• Economy passengers (priority=3) go last

• Use PriorityQueue<Passenger>

5. LinkedList for Browser History

Problem:
Create a browser history with LinkedList<String> that:

• Stores visited URLs

• Allows "back" and "forward" navigation

• Limits history to 10 entries

6. TreeMap for Product Catalog

Problem:
Build a sorted product catalog using TreeMap<String, Double> where:

• Key = Product name

• Value = Price

• Display products alphabetically

• Find the most expensive product

7. Stack for Undo/Redo System

Problem:
Implement text editor undo/redo using two Stack<String>:

• undoStack stores document states

• redoStack stores undone states

8. ArrayDeque for Ticket Booking

Problem:
Simulate a concert ticket booking system with ArrayDeque<String>:

• First-come-first-served queue

• Allow VIPs to cut in line (add to front)

9. Custom Comparator for Employee Sorting

Problem:
Sort a List<Employee>:

• First by department (ascending)

• Then by salary (descending)

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10. WeakHashMap for Cache System

Problem:
Create a memory-sensitive cache using WeakHashMap<String, Image>:

• Automatically removes entries when memory is low

• Ideal for storing temporary image thumbnails

Key Concepts Tested

Question	Collections Used	Core Concept
1	ArrayList	Sorting, removal
2	HashMap	Key-value lookup
3	HashSet	Uniqueness
4	PriorityQueue	Custom ordering
5	LinkedList	Sequential access
6	TreeMap	Auto-sorting
7	Stack	LIFO operations
8	ArrayDeque	FIFO + priority
9	List	Custom Comparator
10	WeakHashMap	Memory management