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By use of the explicit keyword abstract in the class definition, as in Java, D or C#. By including, in the class definition, one or more abstract methods (called pure virtual functions in C++ ), which the class is declared to accept as part of its protocol, but for which no implementation is provided.
An interface in the Java programming language is an abstract type that is used to declare a behavior that classes must implement. They are similar to protocols.Interfaces are declared using the interface keyword, and may only contain method signature and constant declarations (variable declarations that are declared to be both static and final).
Abstract data type for an abstract description of a set of data; Algorithm for an abstract description of a computational procedure; Bracket abstraction for making a term into a function of a variable; Data modeling for structuring data independent of the processes that use it; Encapsulation for abstractions that hide implementation details
An abstract class is either labeled as such explicitly or it may simply specify abstract methods (or virtual methods). An abstract class may provide implementations of some methods, and may also specify virtual methods via signatures that are to be implemented by direct or indirect descendants of the abstract class. Before a class derived from ...
The abstract keyword cannot be used with variables or constructors. Note that an abstract class isn't required to have an abstract method at all. assert (added in J2SE 1.4) [4] Assert describes a predicate (a true–false statement) placed in a Java program to indicate that the developer thinks that the predicate is always true at that place.
Modern object-oriented languages, such as C++ and Java, support a form of abstract data types. When a class is used as a type, it is an abstract type that refers to a hidden representation. In this model, an ADT is typically implemented as a class, and each instance of the ADT is usually an object of that class.
An abstract method is one with only a signature and no implementation body. It is often used to specify that a subclass must provide an implementation of the method, as in an abstract class . Abstract methods are used to specify interfaces in some programming languages.
The Java virtual machine is an abstract (virtual) computer defined by a specification. It is a part of the Java runtime environment. The garbage collection algorithm used and any internal optimization of the Java virtual machine instructions (their translation into machine code) are not specified. The main reason for this omission is to not ...