What is a reflection package?-

In Java, the reflection package refers to the java.lang.reflect package. Reflection is a feature in Java that allows you to inspect or manipulate the runtime behavior of applications. It provides a way to examine or modify the behavior of classes, interfaces, fields, methods, and constructors at runtime.

The key classes in the java.lang.reflect package include:

1. Class: Represents a class or interface.
2. Field: Represents a field (a variable) of a class.
3. Method: Represents a method of a class.
4. Constructor: Represents a constructor of a class.
5. Modifier: Provides static methods and constants to decode class and member modifiers.

Reflection is often used in advanced scenarios such as building tools that analyze or manipulate Java classes dynamically, creating frameworks that work with unknown types, and implementing features like dependency injection. It is a powerful but potentially complex feature that should be used with caution due to its impact on performance and security.