Classes, Arrays & Pointers

Compiler & Linker expectations file1.cppfile2.cppfilen.cpp …. file1.ofile2.ofilen.o …. Linker application (executable) Compiler C++ compiler does not care about filenames.

Classes High level concepts are same as Java – details are bit different. Example: Complex Numbers Unlike Java, – C++ compiler does not care about filenames. – C++ uses 2 files for each class: one header (.h) file for definition, another source file (.cpp) for implementation – Need to use “#include ….h” to use any class.

Concepts: Constructor Constructor – mostly similar to Java – Exception: default values for formal parameters

Concepts: Operator overloading Operator overloading: ComplexNumber x, y, z; z = x + y; In Java?

Concepts: Pass by value or reference Passing parms by value or reference User selection const keyword for reference types Java? Method overloading – similar to Java – use different argument types to differentiate

Concepts: Method overloading Method overloading – similar to Java – use different argument types to differentiate

Concepts: Friend friend designation - breaks OOP philosophy! – specific functions/methods outside the class can access private data  Why?

Concepts: Objects Objects can be created as local variables just like any basic data types. ComplexNumber num1;

Arrays Basic data types and classes are treated the same way in C++, unlike Java. ComplexNumber numbers[5];

Array version #2 ComplexNumber *numbers; numbers = new ComplexNumber[5];

Array version #3 (equivalent to Java) ComplexNumber **numbers; numbers = new ComplexNumber*[5]; for( index i = 0 ; i < 5 ; i++) numbers[i] = new ComplexNumber(…);

Pointers Explicit in C++: ComplexType *cnump; Pointer arithmetic: (cnump + 5) “Address of” operator: & Dereference operator for objects: -> cnump->setComplex(…); Dynamic memory allocation requires pointers (just like references in Java)

Dynamic memory allocation No automatic garbage collection in C++ # of new invocations should match # of delete invocations. If a class constructor allocates memory (i.e. uses “new …”), it needs a destructor method too – it should use “delete …” to release allocated memory.