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There are methods that a subclass cannot override. For example, in Java, a method that is declared final in the super class cannot be overridden. Methods that are declared private or static cannot be overridden either because they are implicitly final. It is also impossible for a class that is declared final to become a super class. [9]
In object-oriented programming, a covariant return type of a method is one that can be replaced by a "narrower" (derived) type when the method is overridden in a subclass. A notable language in which this is a fairly common paradigm is C++. C# supports return type covariance as of version 9.0. [1]
Conventional single-dispatch languages like Java also obey this rule: only one argument is used for method selection (the receiver object, passed along to a method as the hidden argument this), and indeed the type of this is more specialized inside overriding methods than in the superclass.
Call super is a design pattern in which a particular class stipulates that in a derived subclass, the user is required to override a method and call back the overridden function itself at a particular point. The overridden method may be intentionally incomplete, and reliant on the overriding method to augment its functionality in a prescribed ...
These methods are implemented in the same base class as the template method, but with empty bodies (i.e., they do nothing). Hook methods exist so that subclasses can override them, and can thus fine-tune the action of the algorithm without the need to override the template method itself. In other words, they provide a "hook" on which to "hang ...
In C#, a virtual method can be overridden with an abstract method. (This also applies to Java, where all non-private methods are virtual.) class IA { public virtual void M () { } } abstract class IB : IA { public override abstract void M (); // allowed }
final - Declares that the method cannot be overridden in a subclass. native - Indicates that this method is implemented through JNI in platform-dependent code. Actual implementation happens outside Java code, and such methods have no body. strictfp - Declares strict conformance to IEEE 754 in carrying out floating-point operations.
If there are base class methods overridden by the derived class, the method actually called by such a reference or pointer can be bound (linked) either "early" (by the compiler), according to the declared type of the pointer or reference, or "late" (i.e., by the runtime system of the language), according to the actual type of the object is ...