Can we use inheritance in interface?

Also, it is possible for a java interface to inherit from another java interface, just like classes can inherit from other classes. You specify inheritance using the extends keyword. Inheritance will be further discussed below. But unlike classes, interfaces can actually inherit from multiple interfaces.

Is inheritance possible in interface?

An interface contains variables and methods like a class but the methods in an interface are abstract by default unlike a class. Multiple inheritance by interface occurs if a class implements multiple interfaces or also if an interface itself extends multiple interfaces.

Can an interface inherit object class?

Interfaces in java don't inherit from Object class. They don't have default parent like classes in java.

Should I use inheritance or interface?

We can inherit enormously more classes than Inheritance, if we use Interface. Methods can be defined inside the class in case of Inheritance. Methods cannot be defined inside the class in case of Interface (except by using static and default keywords). It overloads the system if we try to extend a lot of classes.

Can we inherit interface in abstract class?

An abstract class defines the identity of a class. An interface can inherit multiple interfaces but cannot inherit a class. An abstract class can inherit a class and multiple interfaces.

Interface Inheritance (implements) | Java | Tutorial 35

Can we inherit abstract class?

An abstract class cannot be inherited by structures. It can contain constructors or destructors. It can implement functions with non-Abstract methods. It cannot support multiple inheritances.

CAN interfaces have static methods?

Static methods in an interface since java8

Since Java8 you can have static methods in an interface (with body). You need to call them using the name of the interface, just like static methods of a class.

Can we override abstract method in Java?

A subclass must override all abstract methods of an abstract class. However, if the subclass is declared abstract, it's not mandatory to override abstract methods.

Can we inherit constructor in Java?

Constructors are not members, so they are not inherited by subclasses, but the constructor of the superclass can be invoked from the subclass.

Can inheritance be applied between interfaces in Java?

Also, it is possible for a java interface to inherit from another java interface, just like classes can inherit from other classes. You specify inheritance using the extends keyword. Inheritance will be further discussed below. But unlike classes, interfaces can actually inherit from multiple interfaces.

Can we have constructor in interface?

No, you cannot have a constructor within an interface in Java. You can have only public, static, final variables and, public, abstract, methods as of Java7. From Java8 onwards interfaces allow default methods and static methods. From Java9 onwards interfaces allow private and private static methods.

Can we inherit one interface to another interface in Java?

An interface cannot implement another interface in Java. An interface in Java is essentially a special kind of class. Like classes, the interface contains methods and variables. Unlike classes, interfaces are always completely abstract.

Can final method be inherited?

Ans) Yes, final method is inherited but you cannot override it. For Example: class Bike{ final void run(){System.

Can an abstract class be a subclass?

Abstract classes cannot be instantiated, but they can be subclassed. When an abstract class is subclassed, the subclass usually provides implementations for all of the abstract methods in its parent class. However, if it does not, then the subclass must also be declared abstract .

Can we override final method in Java?

No, the Methods that are declared as final cannot be Overridden or hidden.

Can we use super keyword in abstract class?

The super keyword does not work here because AbstractClass. m() has been declared abstract, and therefore there is no suitable implementation of it on the parent of the inner class. Remember that inner classes do not extend the outer class (even if it is of the same type), they include a reference to it instead.

Can abstract method be static?

If you declare a method in a class abstract to use it, you must override this method in the subclass. But, overriding is not possible with static methods. Therefore, an abstract method cannot be static.

Can we create constructor in abstract class?

Like any other classes in Java, abstract classes can have constructors even when they are only called from their concrete subclasses.

CAN interface have non abstract methods?

Interface methods are by definition public and abstract, so you cannot have non-abstract methods in your interface.

Can we override default method in interface?

A class can override a default interface method and call the original method by using super , keeping it nicely in line with calling a super method from an extended class. But there is one catch, you need to put the name of the interface before calling super this is necessary even if only one interface is added.

Can we write main method in interface?

Yes, from Java8, interface allows static method. So we can write main method and execute it.

Can static class be inherited?

Static classes are sealed and therefore cannot be inherited. They cannot inherit from any class except Object. Static classes cannot contain an instance constructor. However, they can contain a static constructor.

Why sealed class is used in C#?

We use sealed classes to prevent inheritance. As we cannot inherit from a sealed class, the methods in the sealed class cannot be manipulated from other classes. It helps to prevent security issues.

Can abstract method be private?

If a method of a class is private, you cannot access it outside the current class, not even from the child classes of it. But, incase of an abstract method, you cannot use it from the same class, you need to override it from subclass and use. Therefore, the abstract method cannot be private.

Can constructor be private?

Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.