Constructors

Here's a set of problem statements covering constructors in Java from basic to advanced scenarios:

1. Default Constructor: Create a class named Person with a default constructor that initializes the name to "Unknown" and age to 0.

2. Parameterized Constructor: Define a class named Student with a parameterized constructor that takes name and roll number as parameters and initializes them.

3. Multiple Constructors: Implement a class Rectangle with two constructors: one that takes length and width as parameters and another that takes only one side length (assuming it's a square).

4. Constructor Overloading: Extend the Rectangle class to include overloaded constructors that take different combinations of parameters (e.g., length and width, only length, only width).

5. Initialization Using Constructors: Create a class Circle with a constructor that takes the radius as a parameter and initializes the area of the circle.

6. Constructor Chaining: Implement a class Vehicle with multiple constructors and demonstrate constructor chaining between them.

7. Initialization Using Static Block: Define a class MathConstants with constant values (e.g., PI, E) initialized using a static block in the class.

8. Copy Constructor: Implement a copy constructor in a class Employee that takes another object of the same class and initializes its fields with the values from the given object.

9. Initialization Using Instance Initialization Block: Create a class Book with fields such as title, author, and price, and initialize them using an instance initialization block.

10. Constructor with Varargs: Implement a class Calculator with a constructor that takes a variable number of integers as parameters and initializes an array with those values.

11. Initialization Using Factory Method: Define a class Account with private fields and provide a static factory method to create instances of the class.

12. Constructor with Access Modifiers: Create a class Person with private fields and demonstrate how to initialize them using constructors with different access modifiers.

13. Constructor with Inheritance: Implement a superclass Animal and a subclass Dog, and demonstrate how constructors are invoked in inheritance.

14. Initialization Using Enum Constructor: Define an enum Month with constructors to initialize the number of days in each month and provide a method to get the number of days for a given month.

15. Initialization Using Builder Pattern: Create a class Student with private fields and provide a builder class to construct instances of the student class.

16. Constructor with Final Fields: Implement a class ImmutablePoint with final fields representing x and y coordinates and initialize them using a constructor.

17. Initialization Using Dependency Injection: Design a class Car with fields such as engine and wheels and demonstrate dependency injection using constructor injection.

18. Constructor with Exception Handling: Implement a class DatabaseConnection with a constructor that establishes a database connection and handles any exceptions that may occur during initialization.

19. Initialization Using Properties File: Create a class Configuration that reads properties from a properties file during initialization using a constructor.

20. Initialization Using Reflection: Implement a class ReflectionDemo with a constructor that demonstrates how to initialize fields using reflection in Java.

21. Initialization Using Deserialization: Define a class SerializableObject with fields and demonstrate how to initialize objects using deserialization in Java.

22. Initialization Using Dependency Injection Framework: Create a class UserService with dependencies injected using a dependency injection framework such as Spring.

23. Initialization Using Constructor Annotations: Implement a class Bean with fields initialized using constructor annotations such as @Autowired.

24. Initialization with Lazy Loading: Design a class LazyInitializedSingleton with a constructor that initializes the singleton instance lazily.

25. Initialization with Eager Loading: Implement a class EagerInitializedSingleton with a constructor that initializes the singleton instance eagerly.

26. Initialization with Thread-Safe Singleton: Define a class ThreadSafeSingleton with a constructor that initializes the singleton instance in a thread-safe manner.

27. Initialization with Enum Singleton: Create an enum EnumSingleton representing a singleton and initialize it using an enum constructor.

28. Initialization Using Prototype Pattern: Implement a class Prototype with a constructor that clones objects using the prototype pattern.

29. Initialization Using IoC Container: Design a class ApplicationContext that initializes beans using an Inversion of Control (IoC) container.

30. Initialization Using Module System: Create a module LoggerModule with a constructor that initializes a logger instance using Java's module system.

These problem statements cover a wide range of scenarios for understanding constructors in Java, from basic initialization to more advanced concepts like dependency injection, design patterns, and Java features like modules and reflection.