Java Programming Transparency No. 1-1 Introduction to Java Programming Cheng-Chia Chen September 2001

Java Programming Transparency No. 1-2 Course web page

Java Programming Transparency No. 1-3 Course information  Textbook: None  Main References: The Java Tutorial From Sun Java 2 SDK, Standard Edition Version 1.3 Documentation ) The Java Language Specification Java in a Nutshell 3rd edition,David Flanagan,Oreilly,  References and Documentations: Java Foundation class in a Nutshell, by David Flanagan, Oreilly, The Java Virtual Machine …

Java Programming Transparency No. 1-4 Course information (cont’d)  Some Development Tools and IDEs: Java 2 SDK Version 1.3 (free) BeanShell (free) IBM VisualAge for java (free for entry edition) Kawa IDE (30 days trial) Forte For Java (free for CE) Borland Builder Foundation Version 5 (free) JPad (30 days trial) …  Grading: 4~5 Programming Exercises (40 %) A java Application/System Study report (15~20 %) Final Examination (30%) Class Participation (10~15%)

Java Programming Transparency No. 1-5 Lecture 1. Introduction Cheng-Chia Chen

Java Programming Transparency No. 1-6 Contents 1.What Is Java? 2.Features of Java 3.History of Java 4.Develop first Java program 5.Develop first Java applet

Java Programming Transparency No. 1-7 What is Java? Java is  a programming langugae, defined in The Java language specification (v1,v2,v3)The Java language specification  a virtual machine, Defined in The java virtual machine (v1, v2)The java virtual machine  a plateform Standard edition (jdk): Jdk v1.0~1.02: 8 packages/212 classes jdk v1.1~1.18: 23 packages/504 classes Java 2 (j2se): SDK v1.2~1.22, v1.30: 59 pkg/1520 classes Enterprise edition(j2ee): V1.2, V1.2.1 (May,2000) Micro edition (j2me): v1.0

Java Programming Transparency No. 1-8 What is J2EE ?  What is the Java 2 Platform, Enterprise Edition (J2EE)? a platform that enables solutions for developing, deploying and managing multi-tier server-centric applications. Extend J2SE to a complete, stable, secure, fast Java platform to the enterprise level. A plateform which significantly reduces the cost and complexity of developing multi-tier solutions, results in services that can be rapidly deployed and easily enhanced.

Java Programming Transparency No. 1-9 Benefits of J2EE 1. A unified platform for building, deploying and managing enterprise-class software. 2. Allow enterprise-class application the ability to run anywhere. 3. A platform with a complete range of readily available enterprise-class services. 4. A single easy-to-learn blueprint programming model for J2EE. 5. A platform that is built upon and leverages existing IT investments and guarantees that enterprise-class software will work on multiple platforms.

Java Programming Transparency No Technologies included in J2EE  Enterprise JavaBeans,  JavaServer Pages,  servlets,  the Java Naming and Directory InterfaceTM (JNDI),  the Java Transaction API (JTA),  CORBA,  The JDBC data access API.  Java Message Queue (JMQ)

Java Programming Transparency No What is J2ME ?  1.What is the Java 2 Platform, Micro Edition (J2ME)?J2ME The JavaTM 2 Platform, Micro Edition is the edition of the Java 2 platform targeted at consumer electronics and embedded devices. The J2ME technology consists of a virtual machine (KVM) and a set of APIs suitable for providing tailored runtime environments for consumer and embedded electronics.

Java Programming Transparency No Features of the java language: Java is  simple  object-oriented  distributed  interpreted  robust  secure  architecture-neutral  portable  high performance  multithreaded  dynamic

Java Programming Transparency No Java is SImple  Intentionally created to be syntactically similar to C/C++  Eliminates traditionally troublesome features of C/C++ Pointer arithmetic Multiple inheritance Implicit type coercions Explicit memory management Preprocessor  Eliminates features of C/C++ struct typedef union enum (Programmer controlled) operator overloading  Features included as part of base language: Threads Exception handling

Java Programming Transparency No Java is Object-oriented  Systems are built from sets of classes  Classes are instantiated at runtime to give objects  Objects communicate via messages passing  Everything is part of a class  supported OO Conecpts: Data abstraction and Encapsulation Inheritance Polymorphism Dynamic Binding e.g. variable of Object type can hold everything  Logical cluster of classes == package

Java Programming Transparency No Java is a Distributed language  Network programming support built into JDK class library: TCP sockets UDP packets IP addresses URLs RMI (Remote Method Invocation)  Security features designed into language  Network programming facilities are one of the language's best features.

Java Programming Transparency No Java is an Interpreted language  Source code is initially compiled ( javac ) into architecture-neutral byte-codes  Byte-codes are interpreted by the java virtual machine (JVM) ( java or Netscape)  Dynamic linking/loading (at run time)  (Just In Time) JIT compilers lead to a large performance increase in compilation and runtime execution

Java Programming Transparency No Java is Robust  Strongly-typed language (cf Smalltalk and VisualBasic)  Compile and runtime checking  No pointer arithmetic  Exception handling  Automatic memory management

Java Programming Transparency No Java is secure  Generally very difficult to trick Java's security mechanisms  Depends very much on the program loader (e.g., Netscape)  The SecurityManager class defines the protocol used by the program loader  Access control list

Java Programming Transparency No Java is Architecture-neutral  Byte-codes are architecture neutral  Performance suffers by using bytecodes

Java Programming Transparency No Java is portable  Primitive type sizes are explicit - not architecture dependent  Strings and characters are (16-bit) Unicode compliant  GUI libraries give a native graphic library- independent mechanism for creating quality graphical interfaces (sort of) "They gave us a library that is good for writing programs that look equally mediocre on the different systems." (Core Java, page 9)

Java Programming Transparency No High performance  Interpreting leads to quicker development cycle  Depends what you compare it to "Slightly faster than VB" - (Core Java, page 9) JITC(Just-In-Time Compiler) help greatly in this respect Sun’s Java HotSpot is Newest high performace JIT compiler.  Can use native code for mission-critical performance sections of code JNI: Java Native Interface Sacrifice portability.

Java Programming Transparency No Multithreaded  Based on well-known 20 year old Hoare monitor synchronization  Thread support built into language  Thread synchronization primitives supplied  Garbage collector runs permanently as a low priority background thread

Java Programming Transparency No Dynamic  Class linking, layout, name resolution and object references not resolved until run-time  Runtime Type Information (RTTI) available Can check the type of objects at run-time java.reflect.* package  Class class for dynamic instantiation Can create objects of types unkown until runtime. String sexClassName = getSex(); Object p = Class.forName(sexClassName).instance(); If(p instanceof Male) {…} else if (p instanceof Female) { … } else {… }

Java Programming Transparency No An Example /** * The HelloJava class implements an application that * simply displays "Hello Java!" to the standard output. */ class HelloJava { public static void main(String[] args) { // Display "Hello Java!" System.out.println("Hello Java!"); }

Java Programming Transparency No History of Java  Green Project (1990) Consumer device operating software Requirements: small size, robust, portable, extremely reliable,real- time performance  Oak Originally used C++, then realized a new language was needed Original requirements same as for current language  Java (1993) Intended market never eventuated WWW starting to takeoff Language design "based on" many current OO languages (e.g., C++, Eiffel, Smalltalk, Cedar/Mesa, Objective C) 1995/5/23 Sun launched Java JDK 1.0 released early 1996/1/23

Java Programming Transparency No History of Java  1997 … 2/18: Complete JDK1.1 released 3/28: JDK1.1.1, 5/28: JDK1.1.2, 7/2: JDK1.1.3,…  1998: 9/28: JDK1.1.7, 12/8: J2SE  1999: 6/? J2ME 12/7 J2EE

Java Programming Transparency No Develop your first Java Program and applet 1. Required softwares 2. Creating Your First Application a. Create a Java Source File b. Compile the Source File c. Run the Program 3. Creating Your First Applet a. Create a Java Source File b. Create related HTML files c. Compile and run the Source File

Java Programming Transparency No Required Softwares To write your first program, you will need: 1. The Java TM 2 Platform, Standard Edition. 2. A text editor. Ex:  NotePad,  Ultraedit,  EditPlus2

Java Programming Transparency No Creating Your First Application  The first program, HelloWorldApp, will simply display : “Hello World!".  Steps: Create a Java source file. > Notepad HelloWorldApp.java Compile the source file into a bytecode file. > javac HelloWorldApp.java Run the program contained in the bytecode file. >java HelloWorldApp

Java Programming Transparency No HelloJava.java /** * The HelloWorldApp class implements an application that * simply displays "Hello World!" to the standard output. */ class HelloWorldApp { public static void main(String[] args) { // Display "Hello World!" System.out.println("Hello World!"); }

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Java Programming Transparency No Java 2 SDK Installation Instructions (for WIN32) 1. Download java 2 SDK standard edition 2. Run the Java 2 SDK executable (*.exe). determine where to install j2se. (ex: c:\java\j2se\1.3) > set JAVA_HOME= c:\java\j2se\ Update the PATH variable so that you can type ‘java’ instead of ‘c:\java\j2se\1.3\bin\java’ to invoke javatools. > path=%JAVA_HOME%\bin;%PATH% 4. Check the CLASSPATH variable Used by javatools to determine where to find your personal (nonsystem) java class files Types of java bytecodes (class files):  System : javatools know where to find them.  Extensions: put in %JAVA_HOME%\jre\lib\ext  Personal: via LASSPATH or –cp/–classpath options 5. Start using the Java 2 SDK tools! Java, Javac, javadoc, jdb, javap,…

Java Programming Transparency No Creating Your First Applet a. Create a Java Source File: HelloWorld.java import java.applet.*; import java.awt.*; /** * The HelloWorld class implements an applet that * simply displays "Hello World!". */ public class HelloWorld extends Applet { public void paint(Graphics g) { // Display "Hello World!" g.drawString("Hello world!", 50, 25); }

Java Programming Transparency No Create an HTML file to cntain the applet. A Simple Program Here is the output of my program: The applet does not work!  Save this code to a file called Hello.html.

Java Programming Transparency No Compile and run the program  Compile the Source File. Javac HelloWorld.java  Run the program: With Appletviewer: appleviewer HelloWorld With IE explorer: With Netscape: