> For the complete documentation index, see [llms.txt](https://codewithmeiy.gitbook.io/core-java/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://codewithmeiy.gitbook.io/core-java/test-your-knowledge/constructors.md).

# 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.