Can a subclass be abstract even if its superclass is concrete?

A subclass can be abstract even if its superclass is concrete. For example, the Object class is concrete, but its subclasses, such as GeometricObject, may be abstract. A subclass can override a method from its superclass to define it abstract. In this case, the subclass must be defined abstract.

Can a class override a method and declare it to be abstract?

This is because every child class must override these methods and provide an implementation of them. Thus we can declare these methods as abstract in the parent class.

Can a concrete subclass be declared as abstract?

A concrete subclass can be declared as abstract with abstract key word. A concrete subclass must implement all methods defined in an inherited interface. A concrete subclass cannot be marked as final. The abstract methods cannot be overridden by a concrete subclass.

Can subclasses continue to use an abstract class as its superclass?

You can’t directly use a class that contains an abstract method; you must instead create a subclass that implements the abstract method’s body: To be used, it must be subclassed and its abstract methods must be “overridden” with methods that implement a body.

What happens when a subclass inherits an abstract class?

If the subclass overrides every abstract method that it inherits, then that subclass is not abstract. But, if it inherits any abstract methods and doesn’t override them, then the subclass also has abstract methods and must itself also be defined abstract.

How a subclass can extend an abstract class without implementing superclass abstract methods?

You can define another abstract class and use it as the subclass without needing to implement those methods, however eventually you will find yourself creating a concrete subclass and at that exact point you must implement all the abstract methods, as they are a sort of contract that must be fulfilled.

Can concrete class be a super class?

Concrete Class: A concrete class in Java is a type of subclass, which implements all the abstract method of its super abstract class which it extends to….Difference between Abstract Class and Concrete Class in Java.

What must be true if a subclass of an abstract parent class does not override all of the parent’s abstract methods?

What must be true if a child of an abstract parent class does not override all of the parent’s abstract methods? The child class itself must be declared to be abstract.

Can abstract class have all concrete methods?

An abstract class may contain abstract and concrete methods (i.e with body implementation). Yes, subclasses inherit/override concrete methods from an abstract superclass if they are not private, final or static, they can be overridden.

Can abstract class have non abstract methods?

Yes we can have an abstract class without Abstract Methods as both are independent concepts. Declaring a class abstract means that it can not be instantiated on its own and can only be sub classed. Declaring a method abstract means that Method will be defined in the subclass.

Why a subclass would override a method that has already implemented in its superclass?

The ability of a subclass to override a method allows a class to inherit from a superclass whose behavior is “close enough” and then to modify behavior as needed. An overriding method can also return a subtype of the type returned by the overridden method.

Can a superclass be an abstract class?

We can treat an abstract class as a superclass and extend it; its subclasses can override some or all of its inherited abstract methods.

Can a subclass override an abstract method of a class?

Thus, a subclass must override them to provide method definition. To declare an abstract method, use this general form: As you can see, no method body is present. Any concrete class (i.e. class without abstract keyword) that extends an abstract class must override all the abstract methods of the class.

What is the difference between a concrete and a subclass?

A subclass can override a concrete method and declare it abstract. Of course, because this subclass contains an abstract method, the subclass itself must also be declared abstract. You would then need a further (concrete) subclass to implement the method to be able to instantiate an object.

Can a concrete method be overridden by an abstract method?

Yes, this is allowed. A subclass can override a concrete method and declare it abstract. Of course, because this subclass contains an abstract method, the subclass itself must also be declared abstract. You would then need a further (concrete) subclass to implement the method to be able to instantiate an object.

Can you have an abstract method in a concrete class in Java?

If you declare an abstract method in a class then you must declare the class abstract as well. you can’t have an abstract method in a concrete class. In Java, it is not possible to instantiate an abstract class. An abstract class may contain abstract and concrete methods (i.e with body implementation).