Computer Programming Lecture 11 이윤진서울대학교

Transcription

1 Computer Programming Lecture 11 이윤진서울대학교

2 Slide Credits 엄현상교수님 서울대학교컴퓨터공학부 Computer Programming, g, 2007 봄학기

3 Object-Oriented Programming (2)

4 순서 Java Q&A

5 Java 개요 Object-Oriented Oriented Programming Language (OOPL) by Sun in 1991 Programming with One or More Classes Simple Structuret w/o header files, preprocessor, struct, operator overloading, multiple Inheritance, pointers, etc. Garbage Collection No need to delete or return any storage Dynamic Loading Classes being loaded d as needed d Platform Independence Java Virtual Machine (JVM) Multithreading Support for multiple threads of execution

6 Some Differences with C/C++ Automatic Memory Management Garbage Collector No Dangling gpointers or Memory Leaks No Pointer Handling No Explicit Reference/Dereference Operations No Makefiles No Header Files cf, imported Packages No Function Declaration (Similar to C) No Default Function Argument

7 Java Platform S/W Platform for Running Java - on Top of any Platforms Java Virtual Machine (JVM) Java Application Programming Interface (Java API) Java Platform Java Program Java API Java Virtual Machine Underlying Platform Collection of ready-made software components -grouped into Packages of classes and interfaces)

8 Java Interpreter Implementation of the JVM Executing Java Bytecodes Java bytecodes can be considered as intermediate code instructions for Java bytecodes can be considered as intermediate code instructions for the JVM Java programs, once compiled into bytecodes, can be run on any JVM

9 How a Java Program Runs Compilation and Interpretation Compiler First Translates a Java Program into Java Bytecodes Once Interpreter Parses and Runs Each Java Bytecode Instruction Multiple times on different platforms Java Source Code Java Bytecode Machine Code Java Compiler Java Interpreter Computer javac Java Virtual Machine (JVM)

10 Java Program Saved in Files, Each of Which Has the Same Name as the public Class Containing Only One public Class Containing Other Non-public Classes public class HelloWorld { This code must be saved in HelloWorld.java public static void main(string args[]) { System.out.println( Hello, World ); $ javac HelloWorld.java $java HelloWorld Hello, World compile (create HelloWorld.class; bytecode) start the JVM and run the main method

11 Memory Layout of a Java Program Bytecode of Method Method Area Variables in Class Parameter Variable Stack Local Variable Class Object Array Object Heap String Object Space for objects created by new operator public class MemoryModelTest { static int x=0; public static void main(string args[]) { int a=10, b=20, c; c = add(a, b); static int add(int a, int b) { return(a + b); Sample Program: MemoryModelTest.java

12 Class Unit of Programming Java Program: a Collection of Classes Source code in.java files Description (Blueprint) of Objects (Instances) Common Characteristics Instances Have These Characteristics Attributes (Data Fields) for Each Object Methods (Operations) That Work on the Objects

13 Member Access Control Way to Control Access to a Class Members from Other Classes private Accessible only in the class itself Default (package or friendly) Accessible in the same-package subclasses of the class or in the classes of the same package protected Accessible in the subclasses of the class or in the classes of the same package public Accessible everywhere

14 Object Instance of a Class Uniquely Identifiable Entity w/ Its State, Behavior, and Interface Maintaining Data Values in Its Attributes Referenced by a Reference Variable (of Reference Type) Inheriting from the Class Object w/ a number of methods tostring(), equals(), &, clone()

15 Managing Objects Referencing Objects of Specified Types Objects Created by the new Operator Creating Objects by Executing the Constructors Constructor (Function) Overloading String greeting = new String( hello ); greeting String value = hello Dlti Deleting Objects via Garbage Collection Cll Reference Count for Each Object Cleanup occurs at the convenience of the Java runtime environment

16 Java Example: Abstraction Online Retailer Such as Amazon.Com Item: Type, Title, Maker, Price, Availability, etc. class Item { // Class definition public String title; public double price; Attribute of the class // String is a predefined class // double is a primitive data type public double SalePrice(){ return (price * 0.9); Method of the class Item A = new Item(); // Class object definition and creation Variable of reference type // OKAY : A.title, A.price, and A.SalePrice()

17 Java Example: Encapsulation Online Retailer Example Cont d class Item { public String title; public double price; private int instockquantity; public double SalePrice(){ return (price * 0.9); public boolean isavailable(){ if(instockquantity > 0) return true; else return false; instockquantity attribute is not accessible outside of the Item class Item A = new Item(); // Class object definition and creation // NOT OKAY: A.inStockQuantity // OKAY: A.isAvailable()

18 Java Example: Inheritance Online Retailer Example Cont d class MusicCDItem extends Item { public String singer_name; // Class object definition and creation MusicCDItem B = new MusicCDItem; Item MusicCDItem // OKAY: B.singer_name, B.title, B.price, B.SalePrice(), // and B.isAvailable() // NOT OKAY: B.inStockQuantity

19 Java Example: Polymorphism Online Retailer Example Cont d class Item { public String title; public double price; private int instockquantity; public double SalePrice(){ return (price * 0.9); public boolean isavailable(){ if(instockquantity > 0) return true; else return rn false; public void specificinfo() { System.out.println("no info: a base-class object");

20 Java Example: Polymorphism Cont d Online Retailer Example Cont d class MusicCDItem extends Item { public String singer_name; public void specificinfo(){ System.out.println("signer name=" + singer_name + " : a derived-class object"); public class OnlineRetailer { static void printspecificinfo(item Item){item.specificInfo(); public static void main(string args[]){ Item A = new Item(); MusicCDItem B = new MusicCDItem(); printspecificinfo(a); // Call Item.specificInfo() printspecificinfo(b); // Call MusicCDItem.specificInfo() // - Another derived class (e.g., MovieDVDItem) with specificinfo()

21 Static Modifier Use: Static Attributes & Static Methods Features All Classes Share Static Members It Is Possible to Invoke Static Methods w/o Instantiation In Static ti Methods, It Is Allowed to Access Non-Static ti Data or Non-Static Methods of Classes after the Instantiation of the Objects class A{ private int i = 5; public static printi(){ System.out.println(i); System.out.println(new A().i); // error!

22 Static Modifier Cont d Differences between C++ and Java Static Method Invocation C++ : Class::method(); Java : Class.method(); Static Data Member Initialization C++ : No In-Class Initialization (ANSI/ISO) Java : In-Class Initialization class A{ public: static int i; // declare int A::i = 0; // define & initialize C++ class A{ public static int i = 10; JAVA

23 Windows API

24 순서 Introduction to Windows What is Windows API? Application Development Environments Message Driven System Other Backgrounds Function WinMain Function WndProc API Example : Hello, World! Possible Topics for Final

25 Introduction to Windows History of Windows Windows Windows Windows Windows NT Windows Windows NT Windows Windows Windows XP 07.1 Windows Vista

26 Introduction to Windows Cont d Merits Being the Most Widely Used in Personal Computing GUI : Graphic User Interface Multitasking Standard User Interface User Adapts to New Program Quickly Demerits Very Commercial Product! Not Open Source!

27 [ 참고 ] X Windows : Standard Graphical Engine for Unix/Linux Difference with Microsoft Windows Platform Independent Network Transparent X Protocol o Provide a client-server architecture at the application level o Separate the processing and display for an application - X Server : Low-level interface for controlling screen - X Client : Processing part of the application

28 What is Windows API? API (Application i Programming Interface) Possibly Making Windows System Calls Application 1 Hardware 1 Hardware 2 Windows API Application 2 Windows Application 3

29 Application Development Environments Windows Software Development Kit (SDK) : Providing API Libraries, Documents, Tools, etc. Using API Directly High Performance, Fine-Grain Control Low Productivity Class Libraries Wrapping APIs to Classes Convenient and Powerful E.g., g, MFC (Microsoft Foundation Class) for Visual C++ Rapid Application Development (RAD) Tools Providing Users Don t-care Visual Tools High Productivity, but Low Performance E.g., Visual Basic, Delphi, Power Builder, etc.

30 Message Driven System Content of a Message Event Information Change in the System Change between the User and System (User) Action in a Window Role of OS Regarding a Message Inspecting What Events Have Occurred, and Generating the Corresponding Message Enqueuing the Message into a Message Queue Belonging to Each Program

31 Message Driven System Cont d Use of a Message Queue Each Program Has a Message Queue Function WndProc Processes a Message message queue detect generate OS message enqueue an action

32 Message Driven System Cont d Use of the Message Loop Location End of Function WinMain Functionality Dequeuing from the Message Queue Translating If Necessary Delivering to the Event Handler

33 Message Driven System Cont d return false if getting a WM_QUIT message, else return true translate a keyboard input message e.g.,) WM_KEYDOWN & WM_KEYUP WM_CHAR int APIENTRY WinMain( ){ while(getmessage(&message, 0, 0, 0)){ TranslateMessage(&message); DispatchMessage(&message); deliver the message to function WndProc that specifies what to do

34 Message Driven System Cont d OS Application WinMain message queue while(getmessage(&message, 0, 0, 0)){ TranslateMessage(&message); DispatchMessage(&message); WM_PAINT WM_CHAR WndProc switch(message){ case WM_CHAR: break; case default: return DefWindowProc();

35 Other Backgrounds Handles : Variables Distinguishable from Other Resources 32 bit Integer Type Value Those Made by OS, Not the Users Similarly, fd=open() p in Linux Types : HWND, HPEN, HBRUSH, HDC, etc. Represent a Handle of Each Resource

36 Other Backgrounds Cont d Way for Printing Application Win32 API G D I Device Driver Graphic Device Interface Output Device

37 Other Backgrounds Cont d Printing Procedure Get a device context handle for printing on screen HDC hdc = GetDC(hWnd); Print out using the handle via GDI TextOut(hDC,0,0, Hello,5); LineTo(hDC,100,100); 100); : current window instance Release the device context handle ReLeaseDC(hWnd,hDC); hdc)

38 Function WinMain Entry Point of Program Similar to int main(int, char**); int APIENTRY WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance, LPSTR lpszcmdparam, int ncmdshow); hinstance hprevinstance lpszcmdparam ncmdshow Instance handle of window Previous instance handle Currently this is always NULL Command arguments (like argv) Shape of program (minimize, normal, maximize, )

39 Function WinMain Cont d start create & register a window class create a window show the window get a message dispatch a message translate a message WM_QUIT false true end

40 Function WndProc Window Procedure Specify What to Do When an Event Occurs LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wparam, LPARAM lparam); hwnd message wparam lparam Instance handle of window Types of message Additional information of message (different according to message)

41 API Example : Hello, World! Using MS Visual C++ 6.0

42 API Example : Hello, World! Cont d Make a Workspace for the Example Create a Project Select menu : File New Projects specify the project name select Win32 select Win32 Application

43 API Example : Hello, World! Cont d Select a Default Skeleton Code empty code a simple program : having empty functions (WinMain, WndProc, ) a simple program : displaying Hello World! and having a simple menu

44 API Example : Hello, World! Cont d Add a New Source File into the Project Select menu : File New Files select C++ Source File specify the source file name

45 API Example : Hello, World! Cont d Source Code #include <windows.h> LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM); HINSTANCE g_hinst; LPSTR lpszclass="hello, World!"; program title int APIENTRY WinMain(HINSTANCE hinstance,hinstance hprevinstance,lpstr lpszcmdparam,int ncmdshow) { HWND hwnd; MSG Message; WNDCLASS WndClass; g_hinst=hinstance;

46 register a window class SH); create a window OW, API Example : Hello, World! Cont d WndClass.cbClsExtra=0; WndClass.cbWndExtra=0; WndClass.hbrBackground=(HBRUSH)GetStockObject(WHITE_BRU WndClass.hCursor=LoadCursor(NULL,IDC_ARROW); WndClass.hIcon=LoadIcon(NULL,IDI_APPLICATION); WndClass.hInstance=hInstance; WndClass.lpfnWndProc=(WNDPROC)WndProc; WndClass.lpszClassName=lpszClass; register the WndClass.lpszMenuName=NULL; WndClass.style=CS_HREDRAW CS_VREDRAW; RegisterClass(&WndClass); dispatch procedure hwnd=createwindow(lpszclass,lpszclass,ws_overlappedwind CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT, CW_USEDEFAULT,NULL,(HMENU)NULL,hInstance,NULL); ShowWindow(hWnd,nCmdShow);

47 API Example : Hello, World! Cont d while(getmessage(&message,0,0,0)) (&M g 0 0)) { TranslateMessage(&Message); DispatchMessage(&Message); return Message.wParam; message loop

48 API Example : Hello, World! Cont d LRESULT CALLBACK WndProc(HWND hwnd,uint message, WPARAM wparam,lparam lparam) { switch(message) { case WM_DESTROY: PostQuitMessage(0); break; case WM_PAINT: HDC hdc; PAINTSTRUCT ps; send WM_QUIT hdc = BeginPaint(hWnd, &ps); to itself TextOut(hDC, 10, 10," Hello, World!", 14); EndPaint(hWnd, &ps); break; default: return DefWindowProc(hWnd,message,wParam,lParam); return 0; when a window needs repaint pass the message to the default window procedure by default

49 API Example : Hello, World! Cont d Compilation Ctrl+F7 : Compile a Source File F7 : Build a Executable File Ctrl+F5 : Build and Execute the Program without Debugging F5 : Build and Execute the Program with Debugging compile (Ctrl+F7) build (F7) execute the program (Ctrl+F5) go (F5)

50 Possible Topics for Final Unix/Linux C Program Memory Layout File System Interprocess Communication Utilities and Editors Emacs Batch and Shell Programming C Complier and Linker Static vs Shared Library Gdb & Make Modularity and Abstraction in C Software Modular Design

51 Possible Topics for Final Cont d Scoping C Pointers Call by Reference Memory Management in C Possible Errors in Dynamic Memory Allocation Libraries Standard I/O Library Object-Oriented Programming Design Principles C, C++, or Java Programming Static