Object-Oriented Programming (Java) 2014.2.26

1. Object-Oriented Programming (Java) 2014.2.26

2. Course Information Lecturer: 熊运余 Assist ：张乾初 QQ1053240123 Contact: 3149102@qq.com, 18980704280 Course website: http://cc.scu.edu.cn/2226.html 兴趣题目JAVA地图、移动互联网开发 QQ交流群：296340622 2

3. CTE Curriculum 1: Introduction to Information Systems 2: Introduction to Computer Systems 4 : User Centered Design and Testing 3: Object Oriented Programming and Design 7: Database Systems 5: Data Structures and Algorithms 6: System Level Programming 9: Software Specification, Test and Maintenance 10: Software Project Organization and Management 8: Networks and Distributed Computing 3

4. Schedule 学时：64学时 课堂教学：32学时 ，实验：32学时 学分：4学分 4

5. Contents Java Application Basic (2 weeks) Class design and implementing (4 weeks) Advanced class design (2 weeks) File I/O and GUI（2week) Design Pattern（3 weeks） Java Advanced Tech (2 week) 5

6. Emphases Object Oriented concepts including inheritance, polymorphism, abstract classes, and interfaces Object Oriented Designs using UML Advanced Java Class Design Pattern Practice 6

7. Assessment 50% Final Examination; 50% On-class laboratory practice and homework. 7

8. Attendance, Late Work, Repeat Work Attendance: Absences need not be excused. Late Work: It is generally not accepted and receives a zero. In the case of unplanned emergencies, speak to the instructor for a revised due date.  Repeat Work (Retakes): The course will not give makeup. Multiple-choice assessments can be retaken for a higher grade.  8

9. Your Role – Learning With Doing Attend all lectures Attend all laboratory classes Work out the exercise on your own or after a discussion with your group, don’t make copy Come to see me during lecture, consultation hour and laboratory session 9

10. You end up learning more in less time when you are actually doing stuff instead of just reading.

11. Reference Book & Course Material Beginning Java Objects_From Concepts to Code_Second Edition Deitel & Deitel, Java How To Program, Six Edition. Thinking in Java, Bruce Eckel http://java.sun.com (Oracle) http://java.sun.com/docs/books/tutorial/ 11

12. Topics Covered Today Unit 1.1 Java Applications 1.1.1 Applications in Java 12

13. 1. Java Basic JAVA source code is first written in plain text files ending with the .java extension. Those source files are then compiled into .class files by the Java compiler (javac). A .class file does not contain code that is native to your processor; it instead contains bytecodes(字节码) -- the machine language of the Java Virtual Machine. The Java launcher tool (java) then runs your application with an instance of the Java Virtual Machine. 13

14. JAVA Technology 14

15. Platform-Independent 15

16. The Java Platform The Java platform is a software-only platform that runs on top of other hardware-based platforms. The Java platform has two components: The Java Virtual Machine The Java Application Programming Interface (API) 16

17. Java Virtual Machine A Java Virtual Machine (JVM) enables a set of computer software programs and data structures to use a virtual machine model for the execution of other computer programs and scripts. The model used by a JVM accepts a form of computer intermediate language commonly referred to as Java bytecode. 17

18. Java Platform Platforms J2SDK J2EE J2ME Core/Desktop Application,Applet, Swing, Awt Enterprise/Server JSP/Servlet, EJB Mobile/Wireless Midlet (Cell Phone/PDA) Nokia, Motorola, Siemens SDK JBuilder,Sun One Studio IBM WebSphere, WSAD BEA WebLogic, Workshop Sun One Studio Oracle JDeveloper Borland JBuilder, JCreator, or Text Editor 18

19. Difference between Java and C Java is derived from C Many of its syntactic characteristics are similar to C However, there are some huge differences 19

20. Expressions Arithmetic operators are the same:– +, –, *, /, %, ++, –– Numerical type conversion is mostly the same Java spells out divide by zero, NaN (not a number, etc.) C & C++ are machine dependent 20

21. Relational Operators Relational operators work the same way but return different results:– >, >=, <, <=, ==, != In Java, they return values FALSE and TRUE In C/C++, they return values 0 and 1 In C/C++, a value of zero means false any value that is not zero means true E.g., 1, 5, -1000000, 3.14159, 6.626068 × 10-34 Very important! 21

22. Conditional and Bitwise Operators Conditional execution operators are same in Java and C/C++:– ||, &&, ! Bitwise operators are same in Java and C/C++:– |, &, ^ for bit-by-bit operations with a word Shift operators differ a little bit << (left shift)is the same >> (right shift)is machine dependent in C/C++ I.e., whether to fill from left with zeros or sign bits 22

23. Assignment and Unary Operators Assignment operators work the same:– =, +=, -=, *=, /=, &=, |=, ^= The following unary operators are available C/C++ but not in Java ~ invert the bits of a word * pointer creation & pointer dereference sizeof # of bytes in operand or data type -> pointer dereference with field selection There is no pointer in Java. 23

24. Formatted Input & Output Very different between C and Java Very different between C and C++ Handled by library functions in C printf() scanf() getc() putc() Many others! 24

25. printf() – Print formatted data printf("string containing '%' specifiers",expr1, expr2, expr3, …); Copy the string, character-by-character, to the output. When the ith'%' is encountered, treat it as a conversion specifier for converting the value of expri Copy the converted value to the output per instructions encoded in the conversion specifier Return number of characters printed 25

26. printf() conversion specifiers %d or %i Treat expression as a decimal number (with sign) %u Treat expression as unsigned decimal number %f Treat expression as double precision floating point number; print without exponent %e or %E Treat expression as double precision floating point number; print with exponent (base 10) — scientific notation %c Treat value of expression as the code for a single character %s Treat expression as a pointer to a string … Later in this course 26

27. printf() conversion specifiers (continued) Conversion specifiers may optionally contain Right or left alignment in the field Minimum field width (padded on right or left) Precision – i.e., Maximum length of string Number of decimal places of floating point value Examples %6d – print signed decimal number in 6-char field %8.4f – print floating point number with four places after decimal point, field width of 8 characters 27

28. scanf() – Scan formatted data scanf("string containing '%' specifiers",&var1, &var2, &var3, …); Scan the input, matching the string character by character. When the ith'%' is encountered, treat as a conversion specifier for converting next sequence of characters and storing result in vari Copy the converted value to the output per instructions encoded in the conversion specifier Stop if input does not match string or conversion not successful Return number of successful conversions. 28

29. scanf() – Typical Usage int j; double x; scanf("%d%f", &j, &x); Scan the input, skipping blanks and tabs Try to match a signed integer; if successful, store result in j Continue scanning, skipping blanks and tabs Try to match a floating point number. If successful, store in x Return number of items stored. 29

30. Primitive types In C, the primitive types are referred to using a combination of the keywords char, int, float, double, signed, unsigned, long, short and void. The allowable combinations are listed below, but their meanings depend on the compiler and platform in use, unlike Java. unsigned int unsigned char Java primitive types long (8bytes) int (4bytes) double (8bytes) float (4bytes) boolean (true, false) char (2bytes) 30

31. Classes instead of structures C structure is like a Java class, and all parts are visible to any code that knows the declaration. For example in C: struct point { int x, y; }; 31

32. Type aliasing New names or aliases for existing types may be created using typedef. For example: typedef int int32_t; There is no equivalent of type aliasing in Java. 32

33. Preprocessing There is no equivalent of preprocessing in Java Macro #define PI 3.1415926 Header file #include "mydecls.h" Conditional compilation #if #else 33

34. Enumerations and Unions In C enum light { RED, REDAMBER, GREEN, AMBER }; union number { char c; int i; float f; double d; }; Java 1.5 has introduced a new enum family of classes with greater type-safety, and a few other nice facilities. Java does not have unions. 34

35. Global Variables In C extern int giNumOfPoints; In Java class Contour { public static int iNumOfPoints; } usage of the variable: Contour.iNumOfPoints There is no attribute definition outside class in Java. Java is a pure object-oriented programming language. (attribute/method) 35

36. 2. Applications in JAVA Java programs can be called from Web pages or run stand alone. When launched from a Web page, the program is called a Java “applet.” (JavaScript) When a non Web-based Java program is run on a user's machine, it is a stand-alone Java "application." When running in a Web server, it is a Java "servlet." (JSP/Servlet, JSF, Portlet, J2EE/EJB,Web Services, JNLP) 36

37. Applications An application is a stand-alone program that runs locally. Applications can use console I/O, or can have a GUI developed using the Java class library. Applications have no system resource restrictions. 37

38. Running a Java Application You save the file with a .java extension You write Java code using an editor Text Editor Java code: MyProg.java You run the Java compiler 'javac' javac MyProg.java This creates a file of bytecode with a .class extension Bytecode: MyProg.class You execute the bytecode with the command 'java' java MyProg Output 38

39. Creating an Application  Open "Notepad" (Start  Programs  Other  Notepad)  Type this in: public class MyApplication { public static void main(String args[]) { System.out.println( "This is my first application!"); } }  Save As “MyApplication.java"  Open a DOS Window (Start  MS-DOS Prompt)  Type javac myApplication.java  If you type dir MyApplication.* you should see MyApplication.java and MyApplication.class If it gives an error check you typed it in exactly right. 39

40. Running the Program In the DOS window type java MyApplication D:\> java MyApplication You should see something like this: This is my first application! D:\> 40

41. What does it mean? This line declares a main method. It has one input argument. The operating system begins execution by calling main. This line announces that the program (class) can be run by anyone (public), is called MyApplication. This line tells the computer to display some text ( a string) on the screen. This is what is displayed. public class MyApplication { public static void main(String args[]) { System.out.println( “This is my first application!”); } } 41

42. Java Applets An applet is a little Java program that can run inside a Web browser. It typically shows up inside a rectangular area (which may be transparent) on the browser screen. 42

43. Applet Restrictions Security issues are important, since the provider of an applet may not be trustworthy. Applets can’t touch your system resources (file system, OS, etc.), although some browsers give extra privileges to “trusted applets”. For instance an Applet cannot: Access local files Delete local files Run another program Find out your name Connect to another host Applets can be slow, since the whole thing must be downloaded each time it’s run. 43

44. You save the file with a .html extension Running a Java Applet You can view the applet with the command 'appletviewer' You run the Java compiler 'javac' You write a web page in html using an editor You write Java code using an editor You can view the web page from a web browser This creates a file of bytecode with a .class extension You save the file with a .java extension Bytecode: MyApp.class Window Text Editor Web page: MyApp.html Java code: MyApp.java Text Editor javac MyApp.java Web Browser appletviewer MyApp.html 44

45. Creating an Applet  Open "Notepad" (Start  Programs  Other  Notepad)  Type this in: import java.applet.*; import java.awt.*; public class MyApplet extends Applet { public void paint(Graphics g) { g.drawString("This is an applet!\n", 10, 10); } }  Save As “MyApplet.java"  Open a DOS Window (Start  MS-DOS Prompt)  Type javac MyApplet.java  If you type dir MyApplet.* you should see MyApplet.java and MyApplet.class 45

46. Creating the Web Page • In order to run an applet you have to embed it in a web page using a special <applet> tag e.g: <applet code="name.class" width=www height=hhh></applet> Size of the applet in pixels Using Notepad type in the following and save it as "Greetings.html": <html> <head> <title>Greetings Applet</title> </head> <body> <applet code=“MyApplet.class" width=300 height=200 ></applet> </body> </html> 46

47. Running the Program In the DOS window type appletviewer Greetings.html G:\> appletviewer Greetings.html You should see something like this: 47

48. Running in a Web Browser Open Greetings.html in browser such as Netscape, IE or Firefox, you should see something like: Title Your greeting Message 48

49. What does it mean? This line declares what follows in the { } as a method called paint. This line announces that the program (class) can be run by anyone (public), is called MyApplet and is an Applet. These 2 lines tell the computer to include (import) two standard libraries awt (Abstract Window Toolkit) and applet. This line tells the computer to display some text ( a string) on the screen. This is where it is displayed in pixels across and down from the top left hand corner This is what is displayed import java.awt.*; import java.applet.Applet; public class MyApplet extends Applet { public void paint(Graphics g) { g.drawString("Hello World!", 50, 50); } } 49

50. Things to remember Everything in Java is case sensitive - Paint is not the same as paint. The file containing the source code must have the same name as the class it contains and use the .java extension. For instance: MyApplet should match the name of the file MyApplet.java (not myApplication.java). Curly brackets { and } are used to group parts of the program called blocks together. Blocks can be nested inside other blocks but each { must be matched with a }. Most statements require a semi-colon ; at the end. A statement can continue on the next line if necessary. Spaces are not important - it is recommended to indent blocks for clarity. 50