Can a class extend a class and implement an interface?

A class can extend just one class but it can implement many interfaces. If you use interface as reference type and assign an object of implementing class to it then you can call only those methods that are declared inside the interface.

What does a class must do when implementing an interface?

A class that implements an interface must implement all the methods declared in the interface. The methods must have the exact same signature (name + parameters) as declared in the interface. The class does not need to implement (declare) the variables of an interface. Only the methods.

Is multiple inheritance possible in interface?

The Java programming language supports multiple inheritance of type, which is the ability of a class to implement more than one interface. This means that if a variable is declared to be the type of an interface, then its value can reference any object that is instantiated from any class that implements the interface.

What is the difference between extends and implements keyword?

Differences between extends vs implements extends keyword is used to inherit a class; while implements keyword is used to inherit the interfaces. A class can extend only one class; but can implement any number of interfaces. A subclass that extends a superclass may override some of the methods from superclass.

Is False a keyword in Java?

The true false and null − True, false and null represents certain values in Java, they are used as literals. They are not considered as keywords.

Is it compulsory to override all methods of interface?

Yes, it is mandatory to implement all the methods in a class that implements an interface until and unless that class is declared as an abstract class. Declare the class as an abstract class, as a result, forces you to subclass the class (and implement the missing methods) before you can create any objects.

What happens if a class does not implement all members of an interface?

If you don’t implement all methods of your interface, than you destroy the entire purpose of an interface. We can override all the interface methods in abstract parent class and in child class override those methods only which is required by that particular child class.

When to implement an interface and extend a class in Java?

There is a rule in java if want to implement an interface and extend a class we must extend a class first then we implement an interface When the Java compiler turns a class into bytecode, it must first look to a parent class.

Which is the correct way of implementing an interface a by Class B?

Which of the following is the correct way of implementing an interface A by class B? Explanation: Concrete class implements an interface. They can be instantiated. 3. All methods must be implemented of an interface. Explanation: Concrete classes must implement all methods in an interface. Through interface multiple inheritance is possible.

Can a class extend more than one class in Java?

In Java, multiple inheritances are not allowed due to ambiguity. Therefore, a class can extend only one class to avoid ambiguity. Implements: In Java, the implements keyword is used to implement an interface. An interface is a special type of class which implements a complete abstraction and only contains abstract methods.

Which is an example of an interface in Java?

Here Hello class extends Add class, so methods of Add class “addMethods” can use in Hello class with creating the object. You can also Java Extends interface, here is an example of how to do Extends Interface in Java. But remember Interface can “extend” only interface not a class.