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That algorithm enforces two constraints: children precede their parents and if a class inherits from multiple classes, they are kept in the order specified in the tuple of base classes (however in this case, some classes high in the inheritance graph may precede classes lower in the graph [10]). Thus, the method resolution order is: D, B, C, A.
Composition over inheritance (or composite reuse principle) in object-oriented programming (OOP) is the principle that classes should favor polymorphic behavior and code reuse by their composition (by containing instances of other classes that implement the desired functionality) over inheritance from a base or parent class. [2]
The class A serves as a base class for the derived class B, which in turn serves as a base class for the derived class C. The class B is known as intermediate base class because it provides a link for the inheritance between A and C. The chain ABC is known as inheritance path. A derived class with multilevel inheritance is declared as follows:
Not all languages support multiple inheritance. For example, Java allows a class to implement multiple interfaces, but only inherit from one class. [22] If multiple inheritance is allowed, the hierarchy is a directed acyclic graph (or DAG for short), otherwise it is a tree. The hierarchy has classes as nodes and inheritance relationships as links.
Since JDK 1.2, Java has included a standard set of collection classes, the Java collections framework Doug Lea , who also participated in the Java collections framework implementation, developed a concurrency package , comprising several concurrency primitives and a large battery of collection-related classes. [ 19 ]
Decorator UML class diagram. The decorator pattern can be used to extend (decorate) the functionality of a certain object statically, or in some cases at run-time, independently of other instances of the same class, provided some groundwork is done at design time.
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.
C++ does not have the keyword super that a subclass can use in Java to invoke the superclass version of a method that it wants to override. Instead, the name of the parent or base class is used followed by the scope resolution operator. For example, the following code presents two classes, the base class Rectangle, and the derived class Box.