[计算机软件及应用]ssd3-Chapter1.ppt

Chapter 1 Objects and Classes Contents Introduction to Object Orientation Objects Classes Classes and Objects in Java Composition Java API Introduction Library System 1.1 Introduction to Object Orientation Computer history John Von Neuman , the architecture of computer 1945 Gordon Earle Moore 1965 Moores Law, 1968 create Intel. Computer history Computer history Computer history Computer history Larry Page Sergey Brin. 1998 create Google. Mark Zuckerberg. 2004 create facebook. Cash per employee for tech companies Device in Microsoft 9 prediction about computer(1) 9 prediction about computer(2) Program history Machine code Assembly Language Procedural Programming OO SOA? Abstraction Levels of Abstraction Procedural Programming Get often-used common code, and write them as “functions” or “procedures” Functions take inputs and return outputs e.g., sin( x ), or capitalizeString( s ), isANumber( s ) The main program is still a straight sequence of instructions, but it is now shorter because we can now call functions instead of writing the code all over again Disadvantage （1） Functions can access global data with no limitation; There is no relationship between function and data; Disadvantage （2） A lot of Links make： Program Structure is not clear； Program is difficult to modify； Object Oriented Object Oriented Put datas and operations together to construct an object which cannot be devided. From the objects of a same type, abstract out their common attributes to form a Class. Most data in a class can only be operated in its own class. Class interact with outside by interface. Objects communicate with each other by messages. Features of OOP Information hiding Data abstraction Dynamic binding Inheritance Benefits of OOP Modularity -- autonomous entities, cooperation through exchanges of messages Deferred commitment -- the internal workings of an object can be redefined without changing other parts of the system Reusability -- refining