1. Object-based Programming Intuitive explanation Two concrete examples Calculators addition BMI Programming Environment

2. Computer Vs Program Model CPU Program Compiler ???

3. Structuring in Scripts Speech IntroductionConclusionBody Paragraph 1Paragraph 2 Sentence 1Sentence 2 Script components are abstract So are program components

4. Manufactured ObjectsNatural Objects Program Components ~ Physical Objects ~ Program Objects

5. Program Objects ~ Manufactured Objects Program Object add subtract methods execute invoke call manufactured by accelerate brake operations perform Class instance of Program Object

6. Classification through Factories manufactured by

7. Classification through Classes ASquareCalculator Instance ASquareCalculator instance of ASquareCalculator Instance ABMICalculator Instance ABMICalculator instance of ABMICalculator Instance

8. A Simple Class public class ASquareCalculator { public int square(int x) { return x*x; }

9. 2.2 Nature of a Function Domain/Parameter Values Range/Result Values Mapping 1 4 2 3 1 9...

10. Mathematics Vs Java Function Syntax Inspiration for Functional Languages square: I  I square(x) = x 2 Mathematics public int square(int x) { return x*x; } Java

11. Instantiating ASquareCalculator

12. ASquareCalculator Instance

13. Invoking a Method

14. ABMICalculator Body Mass Index weight height 2 (kg) (metres) public class ASquareCalculator { public int square(int x) { return x*x; } public class ABMICalculator { public int calculateBMI (int weight, int height) { return weight/(height*height); }

15. Bare Bone Environment MS-DOS Prompt (Command Interpreter) Notepad (editor) Jvc (J++ compiler) Jview (J++ interpreter) ObjectEditor

16. Creating MS-DOS Prompt Window

18. Using Notepad to Edit Autoexec notepad C:\autoexec.bat

19. Setting Path and Classpath Path List of Command Directories Must have Jvc and Jview Directories Class Path List of Library Directories, Jar Files, Zip Files Add oe.jar, shapes.jar, swingall,jar

20. Setting Path and Classpath SET PATH=%PATH%;C:"\Program Files\Microsoft Visual Studio\VJ98" SET CLASSPATH=%CLASSPATH%;.;D:\Java\lib\oe.jar;D:\Java\lib\shapes.jar;D:\Java\lib\swingall.jar Reboot! previous classpath current directory jar files may be zipped

21. Check After Reboot

22. Developing BMI Program

23. Interacting with ObjectEditor

25. Program Development Process Text Editor ABMICalculator Source Code creates Java Compiler reads ABMICalculator Object (Byte) Code creates Java Interpreter ABMICalculator Instance calculateBMI instantiates calls ObjectEditor main calls

26. Class Header Class Body Anatomy of a Class 2. 3. 4. 5. 6. 7. { { } 1. } Access Specifier public class ABMICalculator Method Header Method Body public double calculate BMI(double weight, double height Return Type Return Statement return Return Expression weight/(height*height); Parameter Name Parameter Type

27. Formal Vs Actual Parameters parameters actual public double calculateBMI(double weight, double height) { return weight / (height*height); } parametersformal Invoke method weight 0 height 0 variablesmemory assigned 74 1.77

28. Errors class ABMICalculator { double calculateBMI(double weight, double height) { return (height*heigh)/weight } Syntax Error Semantics Error Logic Error Access Error

29. Class Access Error

30. Method Access Error

31. User Error

33. JVC Error Reporting ABMICalculator.java (3,3) : error J0232: Expected '{' or ';' ABMICalculator.java (3,3) : error J0021: Expected type specifier ABMICalculator.java (3,3) : error J0019: Expected identifier ABMICalculator.java (5,1) : error J0020: Expected 'class' or 'identifier' Line no char. no

34. Case Conventions Start variable name with lowercase letter (weight). Start class name with uppercase letter (ABMICalculator) Start each new word with upper case letter (ASquareCalculator)

35. Object Editor Changes Case calculateBMI()

36. Identifiers Reserved Words/KeyWords double, class, int, public, return boldface Programmer-defined Names Variable Names Class Names First character is letter Other characters:letter, digit, _ calculateBMI2 calculate_BMI