Java Constructors – Real-World Case Study

🎯 Concept Overview

Type	Purpose
Default Constructor	No parameters, provides default initialization
Overloaded Constructor	Multiple constructors with different parameters for flexible object creation
Constructor Chaining	One constructor calls another using this(...) to reduce code repetition

🏨 Real-World Scenario: Hotel Room Booking System

Let’s say you're building a hotel reservation system, where users can book rooms of different types.Some bookings come with default details, while others are fully customized.

🔹 Java Code Example: HotelRoom with Constructor Variants public class HotelRoom {

private String roomType;

private double pricePerNight;

private boolean hasBreakfast;

// ✅ Default constructor

public HotelRoom() {

this("Standard Room", 1500.0, false); // Constructor chaining

}

// ✅ Constructor with one parameter

public HotelRoom(String roomType) {

this(roomType, 1500.0, false);

}

// ✅ Constructor with two parameters

public HotelRoom(String roomType, double pricePerNight) {

this(roomType, pricePerNight, false);

}

// ✅ Full constructor (master constructor)

public HotelRoom(String roomType, double pricePerNight, boolean hasBreakfast) {

this.roomType = roomType;

this.pricePerNight = pricePerNight;

this.hasBreakfast = hasBreakfast;

}

// ✅ Method to display details

public void displayDetails() {

System.out.println("Room Type: " + roomType);

System.out.println("Price/Night: ₹" + pricePerNight);

System.out.println("Breakfast Included: " + (hasBreakfast ? "Yes" : "No"));

System.out.println("-----------------------------");

}

} 🔹 Usage in main() public class Main {

public static void main(String[] args) {

HotelRoom room1 = new HotelRoom(); // Default

HotelRoom room2 = new HotelRoom("Deluxe Room"); // Name only

HotelRoom room3 = new HotelRoom("Suite", 3500.0); // Name + price

HotelRoom room4 = new HotelRoom("Presidential Suite", 9000.0, true); // Full

room1.displayDetails();

room2.displayDetails();

room3.displayDetails();

room4.displayDetails();

}

} 🧠 Step-by-Step Explanation

Feature	Explanation
Default Constructor	Creates a standard room with preset values. Ideal when no customization is needed.
Overloaded Constructors	Supports various use cases: name-only, name + price, full control.
Constructor Chaining	Ensures all paths eventually route to the main constructor, centralizing initialization logic.
Real-world analogy	Hotel booking system where user can: – accept defaults – choose room name – or set custom preferences

💬 How to Explain in Interview

"In the hotel booking model, I used overloaded constructors to allow flexible room creation: from a fully default room to a highly customized one. I used constructor chaining (this(...)) to route all variants to the master constructor, which ensures consistent logic, reduces redundancy, and makes the code maintainable."

💡 Design Insights

• 🔁 Avoids duplication – central logic lives in one constructor

• 🧱 Scalable – easy to add new features like hasWiFi, roomNumber

• ✅ Clean code – chaining enhances readability and maintenance
  

🧪 Interview Questions to Expect

Question	Example Answer
What is constructor chaining and why is it useful?	It's when one constructor calls another using this(...). It centralizes initialization logic, avoids code duplication, and makes updates easier.
What happens if no constructor is defined?	Java provides a default constructor only if no other constructor is defined.
Can constructor call a method inside it?	Yes, but avoid calling overridden methods — it may cause unexpected behavior before full initialization.
Can constructors be private?	Yes — typically used in Singleton pattern or with Factory methods to control object creation.

🛠️ Student Practice Challenge

Task: Create a class FlightTicketInclude the following:

• Fields: String passengerName, String flightClass, double basePrice, boolean isInternational

• Constructors:

  • Default (Domestic, Economy, ₹5000)

  • With passengerName only

  • With name and class

  • Full constructor with all fields

• Method: calculateTotalPrice() (Add ₹2000 if international)