java_intro by bdmantra

VIEWS: 2 PAGES: 14

									22-Oct-10
 Java is a programming language: a language that you
  can learn to write, and the computer can be made to
  understand
 Java is currently a very popular language
 Java is a large, powerful language
   but it is not simple!
 Compared to C++, Java is elegant




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 A declaration gives some information to the computer
 A statement tells the computer to do something
   Statements should really be called “commands”
 Comments are ignored by the computer—they are
 explanations of your program for human beings to
 read




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 Syntax is the “grammar” of the language
     The syntax of Java is large, but finite
     Syntax must be absolutely correct
     The computer will point out every syntax error
     Error messages may be helpful or misleading
 Semantics is the “meaning” of your program
   Semantic errors cause your answers to be wrong
   You may or may not get error messages




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 Java has syntax and semantics
   This is where you begin
   It is possible to learn everything about Java’s syntax and
    semantics
   We will cover most of Java’s syntax and semantics
 Java also has “packages”
   Packages are sort of like vocabulary bundles
   To be good at Java, you need to learn many packages
   There are more Java packages than you can ever learn




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ACTIONS:              logic errors


                  runtime error

             syntax errors

      edit           compile          run (execute)
                          ok                       ok

THINGS:                                                           ok
             .java           .class   input data
                                                        results
              file            file    (optional)



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 Java 1
   Java 1.0: Original, not very good version
   Java 1.1: Greatly revised and improved
 Java 2
   Java 1.2: Includes “Swing”
   Java 1.3: More new packages, no new syntax
   Java 1.4: Introduces the assert statement
 Java 5
   Java 1.5: Available as beta; several additions to syntax


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 JRE, Java Runtime Environment
   This is the software that allows you to run Java programs
    on your computer
 SDK, System Development Kit (previously called JDK,
 Java Development Kit)
   The software that allows you to create and run Java
    programs on your computer
   When you install the SDK, you get a JRE along with it
 IDE, Integrated Development Environment
   A tool that makes it easier to write programs


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 Beta software
   Software that is new, untested, often buggy
 Interface
   the place where things touch each other
   the way that distinct things communicate
 GUI, Graphical User Interface
   A way for the computer and the user to communicate via
    graphics (pictures) on the screen




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 BlueJ is an IDE (Integrated Development Environment).
 It includes
   an editor, which you use to write your programs
   a debugger, to help you find your mistakes
   a viewer, to see the parts of your program
   an easy way to run Java programs
   an easy way to view documentation




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 Powerful software can do everything you want to do-
    -for example, Microsoft Word
   Complex software is hard to learn and hard to use--
    for example, Microsoft Word
   More power usually means more complexity
   Elegant software somehow manages to be both
    powerful and simple
   BlueJ is elegant



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 128 MB of RAM (256 MB recommended)
 500 MHz Pentium or better
   Macintosh: must run Mac OS X
 Java JDK 1.4.2 or 1.5 (includes JRE)
 BlueJ 1.3.5 or 2.0
   Earlier versions of BlueJ have serious problems
   If you have an older version, update!
 By the way: the SDK and BlueJ are free




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 If you plan to use your own computer:
    Download and install Java JDK (=SDK) 1.5
      http://java.sun.com/j2se/1.5.0/download.jsp
      Find where it says Download J2SE 5.0 RC and click
       DOWNLOAD in the JDK column
      If you have a Macintosh, get Java 1.4.2
        http://java.sun.com/j2se/1.4.2/download.html
   [Optional, but strongly recommended] Download
    the Java documentation from the same page
   Download and install BlueJ 1.3.5 or newer
      http://www.bluej.org/
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