Java教程英文版.ppt

1、Java,How to find, install and begin to use the Java programming language.,A word or two on the history of some old fashion programming languages A small history of Java How do I install it on my computer? How do I use what I just installed?,What were going to cover,A short look at some old school la

2、nguages, BASIC, C and C+ It all begins in the sixties,BASIC,BASIC stands for Beginners All-purpose Symbolic Instruction Code. It was designed in 1963 at Dartmouth college. It was designed to make it easy for non-technical people to write computer programs.,BASIC programs were like grocery lists. You

3、 told the program what you wanted to do and it did it in order. BASIC was Interpreted.,C and C+,Developed in the early seventies, “C” became the de-facto language for microcomputer programming in the seventies and eighties. “C” was not interpreted, it was compiled. _ Later, in the early eighties, C+

4、 introduced object orientation to the C world. Originally called “C with Classes”, Bjarne Stroustrup developed the additions to C that, in 1985, became C+. OO is when programmers try to mimic the real world more closely and make programs act like “objects” and not just be grocery lists.,So, what hav

5、e we learned?,BASIC was an interpreted programming language “C” was a compiled programming language “C+” brought object orientation to “C”,Say goodbye to the seventies and welcome to a short (but hopefully informative) history of the Java programming language,Authentic Seventies Nerds,James Gosling

6、began developing Java beginning in 1991 It was first called “Project Green” and Oak” First developed for remote cable TV boxes James Naughton creates “HotJava” in 1995. its a web browser that lets you run “Applets”. The entire browser is written in Java. In 1998 Java 1.2 is released Java just releas

7、ed version 1.6 or J2SE 6,James Gosling Circa 1971,James Gosling Today,Java Buzzwords,Simple Object Oriented Architecture Neutral Portable Multithreaded High Performance JIT Buzzwords glommed from the Core Java 2 book verbatim,FREE,Is Java Interpreted or Compiled?,Is Java Interpreted or Compiled?,BOT

8、H!,Java programs are compiled to Bytecode,Bytecode is then interpreted by a JVM, or Java Virtual machine. The virtual machine is what runs your program,Its the JVM that cares about your Operating system, NOT THE PROGRAM! WORA - Write Once, Run Anywhere!,Is Java Object Oriented?,Is Java Object Orient

9、ed?,YES!,Every bit of code in a Java program is in a “Class”,Code Reuse, Encapsulation, Polymorphism, Inheritance,DUKE!,Why? Who knows,Downloading a Java JDK,You want a JDK, not just a JRE Create a “Temp” directory on your PC or laptop Go to Go to the “Popular Downloads” section and select “Java SE”

10、 Select a JDK without Netbeans (Well talk about this later) Agree to the accept the use policy Right Click and Save the Offline Windows JDK to your temp dir,Installing a Java JDK,Go to your “Temp” dir using Windows Explorer Make sure no other apps are running and double click the install program you

11、 just downloaded. Follow the steps. I install in C:Java Watch fom multiple JREs and JDKs! In Windows the Registry runs the show now, not the JAVA_HOME env variable Test with a Command Prompt Window and “java version” Add C:Java”Java ver”bin to your PATH var Be sure to add “current directory” to the

12、CLASSPATH (if you had one),Now, Lets test it,DOS - Command Prompt Make a directory structure Type “Edit” and Voila PSVM Test JAVAC and JAVA Create Bytecode ( the *.class file) with “Javac” Run Program with “Java”,If we were lucky we got something that looks like this,Help on the Web, http:/remus.rut

13、/freestuff Got an Error? Just type it verbatim into Google and you usually can find the answer to your question or solve your problem. Wikipedia is a good place to get background and history On anything, and Java is no exception,Remember.,Java is both compiled and interpreted Java is Object Oriented is Javas home,You want the Java Development Kit (JDK) , not a JRE or J2EE Take your time, use temp directories for setup files Test with a simple “Hello World” after you install Use th