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BPJ444: Business Programming Using Java Introduction

BPJ444: Business Programming Using Java Introduction. Tim McKenna. Introduction. The Focus of BPJ444 What is Java? The Sun Java 2 Platform Getting Started with Java Programming The IBM i5, iSeries, AS/400 Java Platform. The Focus of BPJ444. Java programming skills (85%)

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BPJ444: Business Programming Using Java Introduction

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  1. BPJ444: Business Programming Using Java Introduction Tim McKenna

  2. Introduction • The Focus of BPJ444 • What is Java? • The Sun Java 2 Platform • Getting Started with Java Programming • The IBM i5, iSeries, AS/400 Java Platform

  3. The Focus of BPJ444 • Java programming skills (85%) • IBM tool and platform (15%) • IBM WebSphere Development Studio Client for iSeries which is based on Eclipse IDE. Use Eclipse. • IBM iSeries as a database platform • preparation for other courses • DOMINO, iSeries Practicum, Web Services Architecture

  4. What is Java? • invented at Sun Microsystems in 1991 by James Gosling, a Canadian. • named the new language “Oak” after looking out his office window • later renamed “Java” following a trademark search • 1994: hey, this Web thing is way cool • May 23, 1995: Java and HotJava browser officially announced • JDK 1.0 available November, 1995

  5. What is Java? • Java starts with C/C++ language form: • syntax, semantics, expressions • Java improves C/C++: • no pointers in Java … hooray • no memory manglement malloc/free • Java does automatic “garbage collection” • strings are objects, not null-terminated arrays • int, long, float are the same everywhere • out of bounds array index checking at run time

  6. Java cleans up C++ • no operator or keyword overloading • things mean what you think they mean • no header files • Java uses classes and packages • no multiple inheritance • no standalone functions • in Java, all methods belong to a class • no preprocessor • everything is in the Java language • no structures or unions • everything is in a class

  7. Java is better • for Web, business & application programming (no memory manglement) • safer than C & C++ (no pointer stuff) • rich library of programming features • more portable across platforms • downloadable Java applets can run • in anybrowser (unlike ActiveX) • safely in the Java security “sandbox”(unlike ActiveX)

  8. Java formula • Java = C++ – complexity and ambiguity + security and portability

  9. Java is Object Oriented • focus is on objects, i.e. classes of things • objects have attributes: fields or variables (data) • objects have behaviour: methods to act on data • Procedural languages like C or COBOL … • use algorithms to act on data – trusting all other programs to behave properly and not corrupt data. • data has no control of programs acting on it data's only protection is DB constraints • data and procedures are structurally independent but functionally dependent

  10. The Sun Java 2 Platform • Java mantra: “write once, run anywhere” • the same code runs on any platform • also: run anytime • same code runs on the same platform over time • today on WinXP/Pentium 32bit CISC • tomorrow on Win?? & Itanium 64 bit EPIC • (this has always been OS/400 strength… 1979 S/38 *PGM objects run on current iSeries) • criticism: “write once, test/debug everywhere” • with Java 2, this is rarely an issue anymore. • with C++, it is still true

  11. The Sun Java 2 Platform- how does it do that? • use of bytecode to achieve portability • .java source code ‘compiled’ into .class bytecode • virtual assembler language • Java Virtual Machine interprets standard bytecode and runs it on a specific platform • OS/hardware platform implements its own JVM • e.g. OS/400, Wintel, Mac, Unix, Linux • each have different Java Virtual Machines (JVM) to run standard bytecode on their local OS / hardware • some just-in-time compilation for speed • performance issues everywhere except OS/400

  12. The Sun Java 2 JDK • terminology • JRE: Java Runtime Environment • JDK: Java Development Kit • SDK: Software Development Kit (old name for JDK) • Java compiler: > javac classfile.java • Java interpreter (JVM) > java classfile • other command-line tools (e.g. javadoc, jar) • versions: 1.0, 1.1, 1.2, 1.3, 1.4, 1.5

  13. How to install Java 2 JDK? • http://java.sun.com • link: J2SE Core Java • common problems in installation • path name (“command unknown”) • classpath name (“class file not found”) • upper/lower case names • solutions: JDK documentation, General Information, Installation Notes • see BPJ444 web site for installation notes

  14. How to code, compile and run a Java program? • Java 2 JDK Environment (Windows Platform) • notepad or TextPad: type in Java source code • compile source code: > javac HelloWorld.java • run program: > java HelloWorld • Eclipse: create a project, enter code (with assistance), save a file (auto compiled), run from inside Eclipse…it's an Integrated Development Environment

  15. Getting Started with Java Programming • Two Examples: a Java application and a Java applet • The Anatomy of a Java Application • Java Applets and the Internet • The Anatomy of a Java Applet • The Java Tutorial (online): http://java.sun.com • see the Introduction web page

  16. Definitions • package: a group of related classes • sometimes called a "library" of classes • Java API: Application Program Interface • Java's many packages with many capabilities • all documented with javadoc utility into HTML pages • base package “java.lang” is automatically imported into every Java program

  17. Some Examples • a Java application (console-based) • HelloWorld.java • HelloWorld2.java • command line tools: javac, java • a Java applet • HelloWorldApplet.java • HelloWorlddemo2.html • tools: javac, appletviewer

  18. The Anatomy of a Java Application • Example: HelloWorld.java • three types of comments • line, multi-line, and javadoc • keywords: public, static, private • use of API specification • names: System, out, println • package name: java.lang • the javadoc command: • > javadoc HelloWorld.java • > runJavadoc.bat (in Week01.zip) will organize and document all .java files in a directory

  19. The Anatomy of a Java Applet • a Java program that runs in a web page subject to security restrictions • Example: HelloWorldApplet.java • keyword: import • use of API specification - names: java.applet.Applet, paint • names: packages, classes, method, objects • tools: appletviewer, Firefox

  20. IBM i5, iSeries, AS/400 Java Platform • Sun JDK compliant • the QShell Interpreter and Integrated File System (IFS) – simulated UNIX environment • AS/400 Toolbox for Java • Java classes developed by IBM to access OS/400 resources • performance optimization • the JVM is integrated with OS/400 in microcode • OS/400 Java commands: CRTJVAPGM, RUNJVA

  21. Java and IBM eServer iSeries • Approach 1: use of a workstation (or desktop) • locally develop Java code, e.g. using IBM WDSC • ftp the Java code to the IBM iSeries server Integrated File System e.g. /bpj444demo • use iSeries QShell (STRQSH) to compile & run:cd /bpj444demoset CLASSPATH . javac HelloWorld2.javajava HelloWorld2

  22. Java and IBM eServer iSeries • Approach 2: Use of IBM Operations Navigator • workstation development of Java code • “drag and drop” • from Windows Explorer to Operations Navigator • use an iSeries Integrated File System directory • RIGHT click on HelloWorld2.java to compile the code • RIGHT click on HelloWorld2.class to run the code

  23. Java and IBM eServer iSeries • Approach 3: green screen server environment • use SEU or EDTF to build Java programs • use CL commands to compile and run Java programs. e.g.===> RUNJVA CLASS(HelloWorld2) CLASSPATH('/bpj444demo')===> GO CMDJVA

  24. WebSphere Development Studio Client for iSeries • build on Eclipse technology • open source IDE: www.eclipse.org • tool for developing Java, etc. code • built-in special support for OS/400 Java - AS/400 Toolbox for Java - Enterprise Toolkit for AS/400 • www.ibm.com/software/ad/wdt400/

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