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A snippet of Java code with keywords highlighted in blue and bold font. In the Java programming language, a keyword is any one of 68 reserved words [1] that have a predefined meaning in the language. Because of this, programmers cannot use keywords in some contexts, such as names for variables, methods, classes, or as any other identifier. [2]
For example, a parent class, A, can have two subclasses B and C. Both B and C's parent class is A, but B and C are two separate subclasses. Hybrid inheritance Hybrid inheritance is when a mix of two or more of the above types of inheritance occurs. An example of this is when a class A has a subclass B which has two subclasses, C and D.
It is distinct from single inheritance, where an object or class may only inherit from one particular object or class. Multiple inheritance has been a controversial issue for many years, [1] [2] with opponents pointing to its increased complexity and ambiguity in situations such as the "diamond problem", where it may be ambiguous as to which ...
A sealed class cannot be subclassed. It is basically the opposite of an abstract class, which must be derived to be used. A sealed class is implicitly concrete. A class declared as sealed via the keyword sealed in C# or final in Java or PHP. [38] [39] [40] For example, Java's String class is marked as final. [41]
Classes in Java can only inherit from one class. A class can be derived from any class that is not marked as final. Inheritance is declared using the extends keyword. A class can reference itself using the this keyword and its direct superclass using the super keyword.
Due to the C++ language not having a dedicated keyword to declare interfaces, the following C++ example uses inheritance from a pure abstract base class. For most purposes, this is functionally equivalent to the interfaces provided in other languages, such as Java [ 4 ] : 87 and C#.
Mixins first appeared in Symbolics's object-oriented Flavors system (developed by Howard Cannon), which was an approach to object-orientation used in Lisp Machine Lisp.The name was inspired by Steve's Ice Cream Parlor in Somerville, Massachusetts: [1] The owner of the ice cream shop offered a basic flavor of ice cream (vanilla, chocolate, etc.) and blended in a combination of extra items (nuts ...
There will be sub-classes each of which is derived from one of the super-classes. The sub-classes are mutually linked via fields, and each sub-class may override the methods inherited from the super-class. New methods and fields are usually declared in one sub-class. [1] The following diagram shows the typical structure of multiple inheritance: