a subclass can override a concrete method in a superclass to declare it abstract.

Can a subclass override a concrete method in a superclass to declare it abstract?
A subclass may override a method from its superclass to declare it abstract.
This is rare, but useful when the implementation of the method in the superclass becomes invalid in the subclass.
Of course, this requires the subclass itself to be declared abstract.
What will happen if we do not override all the abstract methods in sub class?
If you don't, a compile time error will be generated for each abstract method (that you don't override) saying “subclass_name is not abstract and does not override abstract method abstractmethod_name in classname”.
An abstract method is a contract which forces its immediate subclass to implement the behaviour of all abstract methods.
Where as overriding is optional and is not always a necessity for the subclasses.
Efficiency of abstract method lies in the fact that they force the immediate subclass to provide implementation.

Can an override method be abstract?

override methods support covariant return types.
In particular, the return type of an override method can derive from the return type of the corresponding base method.
You cannot override a non-virtual or static method.
The overridden base method must be virtual , abstract , or override .

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.

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PDF	Chapter 11 Abstract Classes and Interfaces It is possible to declare an abstract class that contains concrete method overridden to be abstract 8 ▻ A subclass can override a method from its superclass

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6 août 2013 · Concrete methods in abstract classes may call abstract methods, even if there is no implementation of the abstract method in the file – Concrete subclass is required to implement the abstract methods – Can only call superclass method if there is an instantiated concrete object – with the overridden methods

PDF	Lecture Notes Chapter Abstract Classes & Interfaces if a subclass of an abstract class does not implement all the abstract methods, a subclass may override a concrete method from its superclass and declare it to

PDF	Using Abstract Classes 13 sept 2019 · There are situations in which you will want to define a superclass that declares the You can require that certain methods be overridden by subclasses by specifying the concrete methods are still allowed in abstract classes

PDF	Object-Oriented Programming: Polymorphism superclass (which can also point to various –Implement every method they declare ◇All concrete subclasses must override all inherited abstract methods

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Using Abstract Classes - WordPresscom

➢Sometimes you will want to create a superclass that only defines a generalized form that A method that is declared as abstract and does not have implementation is known as Thus, a subclass must override them—it cannot simply use the version defined in the concrete methods are still allowed in abstract classes

PDF	Chapter 11 Abstract Classes & Interfaces - CCSU Computer Science "concrete" superclass (all methods defined, so overriding is always optional) The You can put abstract in an instance method heading if you replace the method's body by a you want each subclass to define all methods in the superclass

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b A subclass reference can be assigned to a superclass variable and a superclass reference can be assigned to a subclass 10 4 Q1: A(n) ______ class cannot be instantiated a final b concrete c abstract d static 10 4 Q3: Declaring a non-abstract class with an abstract method is ANS: d it cannot be overridden

PDF	Chapter 13 Abstract Classes and Interfaces CS165 Colorado State We use abstract methods when the super class is concrete ✦ New abstract methods can be declared in the subclass Concrete method overridden to be

PDF	In this Chapter youll learn: To use overridden methods to effect polymorphism □ To distinguish General propositions do not decide concrete cases —Oliver c) If a superclass declares an abstract method, a subclass must implement that method ANS: False Only a