1. 1 The JAVA Application zJava Applications are similar to C++ programs in that they require a MAIN entry point. However, unlike C++ or Visual Basic, Java Applications require everything emanate from a CLASS. zWe will code examine several Java applications. We will also discuss appropriate coding style and naming conventions

2. 2 zGOALS... zTo identify ALL of the main parts of a Java Application, Syntax Errors zTo code simple applications using the proper Syntax, Style and naming Conventions zTo get comfortable with Code Warrior, Java API Document

3. 3 zBreakdown of the Java Application: zUse our HelloWorld and other applications handed out as a reference zHINT: write comments on these handouts !!!

4. 4 zComments // for a line of comment /* for multiple lines */

5. 5 Java Documentation Comments: zDoc comment --- special type of JAVA comment zA multi line comment starts with /** (insead of /*) & Ends with */

6. 6 Java Documentation Comments: zThese comments can be turned into online HTML documentation by the javadoc program EXAMPLE: /** * @ author David Farrell * @version 1.0

7. 7 Public Static Void Main: zThe main entry point in a Java Application zThe first code to execute zActually, it is a wrapper for the Java Class that is to execute first zThe classname that has PSVM MUST match the filename

8. 8 Standard Output Stream: zUsed to send output to the console System.out.println(“Hello World”); zStandard Java API method from the Java.Lang.System class

9. 9 Standard Output Stream: zStatic Method (does not require instance of System class) OPEN UP JAVA DOC AND GO TO java Lang System and look at the out exit gc & sleep methods

10. 10 Class: The initial class as a wrapper for the entry point to the java application (SPVM) public class HelloWorld {

11. 11 Class Constructor: The method that gets executed when an instance of a class is created Public class Addition { public Addition( ) // empty constructor { } static public void main (String args[ ] ) { new Addition( ) ; // calls the class constructor }

12. 12 Import: zBrings in the prewritten classes for us to use / leverage in our application xvital OO benefit provides conformity & reusability Like Adding a component in Visual Basic

13. 13 Import: import javax.swing.JOptionPane; zWe now have Access to all the methods of JOptionPane

14. 14 Import: zOPEN UP JAVA DOC & GO TO javax swing JOptionPane & look at the showInputDialog method

15. 15 Semi-Colon: zEnd of Code segment identified by a semi-colon ;

16. 16 CW debugger (again): zOpen up the various projects created and use the debugger and zMake changes to cause syntax / compile errors zLook at how these messages are displayed zSystem or Exception Errors ( try & catch )

17. 17 Syntax and Style: zJava is case sensitive zRedundant whitespace is ignored zUse blank lines, indenting for better reading of the code

18. 18 Syntax and Style: zCompiler catches most syntax errors, but not logic errors “bugs” zJava statements and declarations usually end in a semi-colon

19. 19 Syntax and Style: zAll Java reserved words are in Lower Case (see handout) booleancharintnull newtruefalse publicprivateprotected staticclass import iftrycatch zReserved words must be spelled exactly.

20. 20 Syntax and Style: zStart ALL class names with a capitol letter (use names that are nouns) String StringBuffer JOptionPane System

21. 21 Syntax and Style: zInstances of objects start in Lower Case String myString String firstNumber

22. 22 Syntax and Style: zStart all method names with Lower Case, then Upper Case remaining words (first word as a verb – action) println( ) parseInt( ) insert( ) insertObject( )

23. 23 Syntax and Style: zStart all names of variables with a Lower Case letter and subsequent words start w/ Upper Case int number; zCan’t start with a digit. zUse self-explanatory names and follow a naming convention

24. 24 Syntax and Style: zUse all Upper Case for constants final int MAXPOINTS = 200;

25. 25 Syntax and Style: zLine up the brackets { } zBrackets identify the beginning of A class A method A code block (like if and endif)

26. 26 zIndent the Correct way: public class Sample { public static void main(String[] args) { int anumber = 23; for(int x=0; x < 10; x++) { anumber += x; } System.out.println( anumber ); }

27. 27 zIndent the Wrong way: public class Sample { public static void main(String[] args) { int anumber = 23; for(int x=0; x < 10; x++){ anumber += x;} System.out.println( anumber ); } } zWhich one is easier to debug !!!

28. 28 zProject: zCode the 4 projects directly from the handouts zBe able to identify all of the parts of the program that we covered

29. 29 zProject: zUse the debugger and make coding changes, once the program works as intended, see and fix the compile errors zImplement the System methods exit gc & sleep in one or more of these programs

30. 30 zProject: zView the JAVA Doc and look at some of the methods and classes we used

31. 31 TEST IS THE DAY AFTER THE PROJECT IS DUE !!!