What is the purpose of the 'implements' keyword in Java?

A concept in object-oriented programming (OOP) where a new interface is created by deriving or extending from an existing interface. In OOP, an interface defines a contract for classes that implement it, specifying a set of methods or properties that those classes must provide. When one interface inherits from another, it means that the child interface includes all the members of the parent interface and may also declare additional members or override existing ones allowing for code reuse and establishing a relationship between the interfaces. It allows for polymorphism, where objects of a derived interface can be treated as objects of the base interface.

In Java, the 'implements' keyword is used to signify that a class is providing concrete implementations for methods declared by an interface. This allows multiple classes to implement the same interface with varying behaviors while ensuring a consistent method signature.

Interface in Java is a special type of class that does not have any concrete implementation of a method, only method signature. An interface can extend another interface. To inherit from an interface, we use implements keyword followed by interface name.

What is the purpose of the 'implements' keyword in Java? In Java 'implements' keyword is used for inheritance of a collections of abstract methods and constant variables defined in an interface. Interface in Java defines generalize behavior of a real world object in form of abstract methods, which has method signature but no concrete body to express the behavior of the real world object. When a class implements the interface it gives it a concrete body as per its specific requirement of the behavior of the real world object it is representing. Also the class has to give concrete body to all the methods it inherits from the interface which it implements.

In Java, while a class cannot extend multiple classes, it can implement multiple interfaces using the 'implements' keyword. When a class implements these interfaces, it must provide implementations for all the abstract methods defined in the interfaces. As a rule, the interface can't be instantiated. For instance: class Clerk implements Person, Employee { // Code implementation } In this case, the Clerk class inherits all methods and constants from both the Person and Employee interfaces.

A concept that promotes flexibility and code reuse. Interfaces define a contract, and classes implementing the same interface can be treated equally. Objects are referenced by their interface type, allowing dynamic binding of methods at runtime. With interface polymorphism, a method can accept objects of different classes adhering to the same interface, enhancing code flexibility, adaptability, and maintainability. This paradigm ensures that objects can be transparently integrated into a unified structure, adhering to a shared interface and simplifying code organization. Overall, polymorphism through interfaces is a foundation in object-oriented programming that provides a robust mechanism for building modular and extensible software.

Interface enables polymorphism. Polymorphism is the ability of an object to take multiple forms, depending on context. Polymorphism means "one name, many forms".

This is how Java handle RTTI. In C++ methods are not virtual by default and cannot be overriden.Java takes the opposite position. By default methods are virtual , implementing an interface is a contract where the class is meant to override the services defined in the interface. In the example makeSound(Animal a) we can guess that every animal (cat/dog/lion) has a different language so the sound resulting from a makeSound() call will be different depending from the animal.

Another pro of using interfaces is they allow multiple inheritance. Multiple inheritance is not supported in Java, due to ambiguity and complexity but it is supported through interfaces. The reason is interfaces only contain method signatures, not a body. To inherit, you must use implements keyword followed by interface name.

The implements keyword is much powerful and important that what it seems to be. There are multiple reasons. First, by using implements, you can define a common behavior. Second, allows dynamic binding. Third- Enables multiple inheritance.

The implements keyword in Java enforces a class to provide concrete implementations for the methods declared in an interface, promoting code contract, multiple inheritance of interfaces, and supporting polymorphism.