8/17/2023 0 Comments Class diagram staruml exampleThe program will duplicate the data throughout all the instantiated objects, which wastes space and makes maintaining the correct count in all the objects difficult at best.Consider the following problems that arise if we define count as a non- static or member variable: Our approach is simple: define a variable named count to count each object as the program creates it. To help us understand the role static features play in C++ programs, imagine that we want to write a program that counts the total number of objects it instantiates from class. The static keyword may modify attributes and operations alike, and is independent of other modifiers such as public or private. The UML denotes static features by underlining them. Denoting static features in a UML class diagram. Programmers translate the underlining to the static keyword when they translate the UML class diagram to C++. Alternatively, the UML denotes static features with class ownership by underlining the feature in the class diagram. Unless otherwise specified, features in a UML class diagram are non- static and have instance (i.e., object) ownership. The UML provides additional notation to differentiate between the kinds of ownership. The contrast between the two ownerships constitutes a significant difference between static and non- static features. On the other hand, static or class features "belong" to the class. Non- static or class members (attributes and operations) belong to individual instances of the class (i.e., objects). Like Java, C++ implements class variables with the static keyword (please see footnote 1). Whereas member variables belong to specific objects, class variables belong to all instances of a given class. The object-oriented solution we seek is called class variables. We could implement the data as global variables, but we've seen that globals are error-prone, so we seek a more secure, object-oriented solution. However, sometimes programs need to manage data that is accessible by various combinations of many objects (the Pouring Puzzle example presented later in the chapter illustrates this situation). So, in a sense, the object "owns" the member variables, and programs must access them through their owners. Generally, each object instantiated from a class maintains its own distinct copy of each member variable declared in the class. Member function calls are bound to an object.
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