1	Introduction to Java for PL/SQL Programmers
2	Agenda Java Basics More advanced Java concepts Implementing Java Java vs. PL/SQL Why use Java? Deploying in Java
3	Overview For PL/SQL programmers wanting to move to Java, there are some important conceptual differences to understand. Learning Java is more than just learning a new syntax. You need to take an object-oriented approach. This presentation will point out basic differences between Java and PL/SQL along with elements requiring more careful attention.
4	Java Language Fully supports object-orientation Supports multi-tasking Platform independent (code is portable) Enhanced memory management Garbage collection
5	Java Terms Fundamental building block: class Everything is a class Datatypes Primitive (also called simple or built-in) Implemented for performance reasons Each has a sister class User-defined Instance: specific occurrence of an object in a class Variable: instantiation of a primitive datatype
6	Basic Parts of Java (1) Comments /* This is a long comment or multiline comment in Java. / // This is a short comment. --Double dashes don’t work. /* automatically generates Javadoc */
7	Basic Parts of Java (2) Access to objects controlled by keywords public: code can be used anywhere private: access limited to other members of the same class protected: access a class member anywhere except from a non subclass in a different package Executable program blocks Collection of declarations, specifiers, and methods Specifiers modify class visibility and functionality
8	Sample Java Code public class MyFirstExample { public static void main ( String args[]){ System.out.println(“Hello World”); } } First line declares a new class Specifier public { } represent the start and end of each code block Second line declares a method - main() JVM looks for method main( ) when application starts static declaration needed because main() method called before any objects are created void is a declaration of return type Remainder of line used to pass parameters to main()method Third line calls a library
9	Java Primitive Datatypes byte short int long char float double boolean Can only hold a single value Cannot be passed by reference or by using explicit pointers Beware of auto casting of variables Integer = float (auto rounds)
10	Types of Variables Boolean 2 values in Java true and false Character Single byte Can be numeric or character Different from a PL/SQL CHAR String Defines an object Used to declare string variables Implemented in Java as an object StringBuffer Sister class to string Used for character sequences that can change size and/or be modified Numeric For whole numbers long, int, short, byte For fractions float, double
11	Object Concepts Object: instance of a class Objects are passed by reference May be as complex as desired To use a class, must declare an instance of it like any other datatype Ex. Integer age = 38; Each public class definition stored in its own source file Has exactly same name as class with .java file extension Compiled version called a class file (.class) Related class files stored in libraries of packages Stored in zip files (.jar)
12	Inheritance and Polymorphism Object-orientation of Java supports inheritance and polymorphism Inheritance Properties/behaviors derived from parent class (superclass) to child (subclass) Polymorphism Can send a message to an object without concern for datatype Includes overriding and overloading Can add additional keywords to class definitions to provide specific capabilities extends – inherits methods and variables
13	Inheritance & Polymorphism Examples // A parent class for a 2-Dimensional object public class Box { int width = 2; int length = 3; } // A child class for a 3-Dimensional object, which inherits a parent class public class Cube extends Box { int height = 4; int width = 1; //polymorphism - this variable(width) is set to 1. int volume = super.width * length * height; public Cube() { System.out.println("The volume of the cube is: " + volume); } public static void main(String[] args) { new Cube(); } }
14	Variable/Object Declarations In Java – can take place anywhere Still need to set coding standards Should still declare variables and objects as in traditional programming languages Creating objects in “pseudo-declaration” sections makes code more consistent Supports objects created on the fly Code stands out and is easier to maintain Cautions Names may not begin with a number Java is case sensitive
15	Java Arrays Similar to arrays in other languages Collections of objects of similar type May have one or more dimensions (multidimensional) Elements within arrays are accessed by indexes (start at 0) To create an array: Declare a variable Allocate memory Initialize elements
16	Collections Powerful classes provide functionality for grouped objects Dynamic arrays Vectors Linked lists Trees Hash tables Java2 has implemented maps to associate key/value pairs.
17	Global Variables May need methods or variables that are independent of class instantiations Use keyword static Member is instantiated when class is referenced for the first time Act as global variables that are accessed by all instances of the class Also used with main() method in application classes
18	Constants Useful at the variable, method, and class levels Use all uppercase when naming Use keyword final (like CONSTANT in PL/SQL) Variables must be initialized in same statement Class cannot override method in a subclass Class cannot be inherited final only applies to method and class declarations Can be overridden in a subclass
19	Control Statements Java uses traditional control statements if-else, switch, loop Also includes three jump statements break, continue, return Control program flow during run time Loop controls Iterative control structures Control repeated execution of specific code segments for while, do while Functionality can be extended using jump statements Loop portions can be modified to handle almost any valid Java expression
20	Exception Handling Can generate an exception using the keyword throw Other Java exception handling statements: try, catch, throws, finally
21	Interfaces Similar to a PL/SQL package specification Use to specify what a class will do without defining how it will be done Must include a declaration statement for each of the class methods to be implemented Does not include the method bodies and instance variables Methods defined are abstract by definition Allow you to compile code that depends on a class while deferring method bodies until interface is implemented Variable declarations in interfaces are final and static by definition Act as constants shared by all classes implementing the interface
22	Interface Example Interface MyArea { int length = 3; int width = 2; double area(); } class MyBox implements MyArea{ public MyBox() { } double area(){ return (length * width); } } class MyTest { public static void main (String args[]) { MyArea boxArea = new MyBox(); System.out.println("Test box area is: “ + boxArea.area() ); } }
23	Garbage Collection Java handles de-allocation of memory for objects no longer referenced by a variable via the garbage collector Explicit activities (ex. Releasing file handle for given object) handled through finalize() method Called just before object is destroyed No guarantee when finalize() method is executed Can cause problems Program not responsive during collection
24	Java vs. PL/SQL Can’t just learn a new syntax More than just { } instead of BEGIN and END Need an object oriented approach Not always more efficient May need to make design concessions Build upon user-defined datatypes (classes) rather than functions and procedures
25	Java-PL/SQL Comparison Java Example: class MyBooleanOperators { public static void main (String args[]) { boolean myTestCondition = true; if (myTestCondition) System.out.println("My condition was TRUE"); myTestCondition = false; //Now reset test condition to FALSE if (myTestCondition) System.out.println("This line Never prints"); } } PL/SQL Example: BOOLEAN operators may be TRUE, FALSE or NULL. v_test_condition BOOLEAN := TRUE;
26	Java-PL/SQL Comparison Java Examples: The char datatype can only represent a single character or symbol, and may be initialized as follows: // decimal equivalent of letter 'a' char myFirstChar = 97; // using a character char mySecondChar = 'a'; // octal equivalent of letter 'a' char myThirdChar = '\141'; // Unicode (Hex) value for 'a' char myFourthChar = '\u0061' ; PL/SQL Example: The CHAR datatype is a fixed length string. v_string_char CHAR(48) := 'Datatype CHAR is a fixed length string in PL/SQL';
27	Java-PL/SQL Comparison public class MyRatio extends Object { public MyRatio() { int numerator = 5; int denominator = 0; int ratio; try { //The beginning of a try block ratio = numerator / denominator ; //divide by zero } catch (Exception e) { //the start of the catch block e.printStackTrace(); //sends error msg to screen } System.out.println("Printed because the error is handled correctly"); } public static void main(String[] args) { //This is the main method new MyRatio(); //This calls the constructor } }
28	Java-PL/SQL Comparison DECLARE v_numerator INTEGER = 5; v_denominator INTEGER = 0; v_ratio INTEGER; BEGIN BEGIN -- The start of the (try) block -- problem code v_ratio := v_numerator / v_denominator; EXCEPTION --This is like the catch block WHEN OTHERS THEN dbms_output.put_line( 'Exception: ' \|\| SQLCODE \|\|', '\|\| SQLTERM); END; dbms_output.put_line( 'This is printed because the error is handled correctly'); END;
29	Why use Java? Emerging language with many advantages over other programming languages Offers fully object-oriented environment for development and web deployment Improved flexibility Ability to build sophisticated applications Drawbacks Newness Less available technical expertise
30	The Market The world wants Java, Web and Internet applications.
31	Is Java all you need to deploy on the Web? NO!!!! Java Deployment JSP Applet Applications Each alternative requires different tools and languages
32	Moving to a Java-Based Development Environment Don’t abandon old development environment immediately Java is still bleeding-edge technology Java alone is not enough Still need to know HTML, JavaScript, and other editors (FrontPage, Dreamweaver) Keep it simple Oracle Developer uses PL/SQL for both front and back ends
33	Java Applications Required Tools JDeveloper Required Languages Java XML JDBC SQLJ
34	Java Applets Required Tools JDeveloper Apache or IAS Required Languages Java XML JDBC SQLJ
35	JSPs Required Tools JDeveloper Apache or IAS Required Languages Java HTML JavaScript XML, JDBC, SQLJ
36	Contact Information Dr. Paul Dorsey - pdorsey@dulcian.com Dulcian Website: www.dulcian.com Oracle JDeveloper 3 Handbook by Dr. Paul Dorsey & Peter Koletzke Oracle Developer: Advanced Forms & Reports by Peter Koletzke & Dr. Paul Dorsey Oracle8 Design Using UML Object Modeling by Dr. Paul Dorsey & Joseph Hudicka Oracle Designer Handbook by Peter Koletzke & Dr. Paul Dorsey