What are the advantages and disadvantages of using sealed classes in Java?

Sealed classes in Java allow restricting the set of classes that can inherit or implement a given class or interface. This provides stricter control over the type hierarchy.

Advantages:

• Increased type safety: the compiler knows all possible subclasses, simplifying verification and processing.
• Improved support for pattern matching and switch, as all options are known in advance.
• Control over extensibility: you can restrict who can inherit, which helps in architecture.

Disadvantages:

• Less flexibility: cannot add new subclasses outside the predefined list.
• May complicate design if the set of inheritors changes frequently.

Example of declaring a sealed class:

public sealed class Shape permits Circle, Rectangle {}

public final class Circle extends Shape {}
public final class Rectangle extends Shape {}

Thus, sealed classes are useful when you need strict control over the inheritance hierarchy.