Which of the following modifiers cannot be used for methods in an interface?

• A. Public
• B. Static
• C. Abstract
• D. Final

Answer: (D)

In Java, an interface is a reference type that can contain constants, method signatures, default methods, static methods, and nested types. All methods in an interface are inherently public and abstract unless they are marked as default or static.

The important point regarding modifiers in the context of methods within an interface is that the final modifier cannot be used. A final method cannot be overridden by subclasses, which contradicts the purpose of an interface. Interfaces are meant to define a contract that must be implemented by classes that inherit from the interface, allowing polymorphism and flexibility. If a method in an interface were to be marked as final, it would prevent implementing classes from providing their own implementations, defeating the core utility of interfaces.

In contrast, public, static, and abstract modifiers are permissible within an interface. Public is the default visibility for interface methods, static methods can be defined with a body, and abstract methods are the standard expectation since they require implementing classes to provide concrete implementations.