How does using Sealed Interface differ from Enum in Java?

Sealed Interface and Enum in Java serve different purposes, although both restrict the set of permissible implementations.

• Enum is a special type that represents a fixed set of constants. It is ideal when you need to define a limited list of values, such as days of the week or states.

  • All values are listed in one place.
  • Enum automatically supports methods like values(), valueOf().
  • Does not support inheritance (cannot extend an enum).

• Sealed Interface (or Sealed Class) is a mechanism to restrict inheritance hierarchy. It explicitly specifies which classes can implement the interface or extend the class.

  • Allows creating more flexible and extendable hierarchies.
  • Can have different implementations with different logic.
  • Used to control extensibility, for example, in design patterns.

Example:

sealed interface Shape permits Circle, Rectangle {}

final class Circle implements Shape {
    double radius;
}

final class Rectangle implements Shape {
    double width, height;
}

Thus, Enum is a fixed set of values, while Sealed Interface is a way to control who can implement the interface, maintaining implementation flexibility.