292 Object-Based Programming Chapter 8 Fig. 8.3 Fig.
292 Object-Based Programming Chapter 8 Fig. 8.3 Fig. 8.3Fig. 8.FiFi3g. 8.3g. 8.3Accessing privateclass members from client code generates syntax errors. (Part 2 of 2.) Software Engineering Observation 8.10 Class designers need not provide set or get accessors for each private data member; these capabilities should be provided only when doing so makes sense. Software Engineering Observation 8.11 Declaring the instance variables of a class as private and the methods and properties of the class as public facilitates debugging, because problems with data manipulations are localized to the class methods that manipulate that data. 8.5 Initializing Class Objects: Constructors When a program creates an instance of a class, the program invokes the class s constructor to initialize the class s instance variables (data members). A class can contain overloaded constructors to provide multiple ways to initialize objects of that class. Instance variables can be initialized either by a constructor or when they are declared in the class body. Regardless of whether instance variables receive explicit initialization values, the instance variables always are initialized. In such cases, instance variables receive their default values (0 for primitive numeric type variables, falsefor boolvariable and nullfor references). Performance Tip 8.1 Because instance variables always are initialized to default values by the runtime, avoid initializing instance variables to their default values in the constructor. Software Engineering Observation 8.12 When appropriate, provide a constructor to ensure that every object is initialized with meaningful values. When creating an object of a class, the programmer can provide initializers in parentheses to the right of the class name. These initializers are the arguments to the constructor. In general, declarations take the form: ClassName objectReference =newClassName(arguments ); where objectReference is a reference of the appropriate data type, newindicates that an object is being created, ClassName indicates the type of the new object (and the name of the constructor being called) and arguments specifies a comma-separated list of the values used by the constructor to initialize the object. Figure 8.4 demonstrates using initializers and overloaded constructors.
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