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Can a non-abstract class implement an interface?
Interfaces can not extend a class or implement an Interface. An interface can extend another Interface. A non-abstract class which is implementing an Interface needs to follow some rules. This class needs to provide the concrete implementation of all abstract method.
Which method should a non-abstract?
An abstract method has no body. (It has no statements.) It declares an access modifier, return type, and method signature followed by a semicolon. A non-abstract child class inherits the abstract method and must define a non-abstract method that matches the abstract method.
Why would you use an abstract method instead of a non abstract one?
However if you had an abstract method in a non-abstract class, you could instantiate the class and get an object, that would have an unimplemented method, which you would be unable to call. Having an abstract method prevents a class from being instantiated, thus making it a de-facto abstract class.
Can’t have an abstract method in a non abstract class?
Answer: You can’t. It’s kind of the definition of abstract. It’s the same reason you can’t instantiate an object as an abstract class.
When should a class be abstract?
In general, a class should be abstract when you have absolutely no reason to create an instance of that class. For example, suppose you have a Shape class that is the superclass of Triangle, Square, Circle, etc.
Can you use a non-abstract method in an interface in Java?
In Java, interface methods are public and abstract by default. So first option is bad practice. Point is that you can’t use non-abstract methods inside of interface, because they are abstract by default. But in abstract class you can use non-abstract or abstract methods. No, it can’t be done in Java 6 or 7.
Which is optional for declaring a method as an abstract?
In an abstract interface keyword, is optional for declaring a method as an abstract. In an abstract class, the abstract keyword is compulsory for declaring a method as an abstract. An interface can have only public abstract methods. An abstract class has protected and public abstract methods.
Which is the best definition of an abstract class?
A class which has the abstract keyword in its declaration is called abstract class. Abstract classes should have at least one abstract method. , i.e., methods without a body. It can have multiple concrete methods. Abstract classes allow you to create blueprints for concrete classes.
Can a interface inherit an abstract class in Java?
An interface can inherit multiple interfaces but cannot inherit a class. An abstract class can inherit a class and multiple interfaces. An interface cannot declare constructors or destructors. An abstract class can declare constructors and destructors.