FilterSystem

A simple yet powerful console-based toolkit for filtering and grouping people data based on age, sex, and nationality.

🚀 Features

🍺 Alcohol Filters

• Filter people who can drink alcohol in Germany (age 16+)
• Filter people who can drink alcohol in USA (age 21+)
• Filter people who can drink alcohol in Afghanistan (age 14+, male only)
• Each filter returns a new array with only the matching people

🗣️ Language Filter

• Filter people who can freely speak English
• Includes citizens of USA and Canada

📦 Grouping with HashMap

• Group by passport strength — Afghanistan goes under WEAK, USA, Canada and Germany go under STRONG
• Group by sex — splits people into MALE and FEMALE lists
• Group by age — calculates average age and splits into YOUNG (below average) and OLD (above average)
• Count English speakers — returns a map with true (USA & Canada, age 4+) and false (everyone else)

🖨️ Print Utilities

• Print any people dataset directly to the console
• Universal printMap() method works with any grouped result

🧠 Concepts Covered

• Enums for type-safe data (Sex, Nationality, PassportStrength, Adulthood)
• Arrays vs ArrayList — when and why to use each
• HashMap as a key-value data structure for grouping
• DRY principle — reusable methods instead of repeated code
• Single Responsibility — each class has one clear purpose
• Autoboxing — difference between int and Integer, boolean and Boolean

▶️ How to Run

1. Clone the repository
2. Open in IntelliJ IDEA
3. Run Main.java