meeting -*- outline -*-

        Bring computer

* Running Java

  Goal is to deal with practical matters,
  running Java, and Eclipse

  Tell them to read the course web page about running Java:

       http://www.cs.iastate.edu/~cs362/running_java.shtml

** Getting it

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             GETTING JAVA

Already on department Linux machines, in

   /usr/java/j2sdk/

For home, go to http://java.sun.com
and get J2SDK 1.4.2

What you get:

    javac    - compiler
    java     - interpreter (virtual mach.)
    jar      - archiver
    javadoc  - HTML page creation
    ...

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** Hello World

Write, compile, and run the simpliest program

------------------------------------------
    SUMMARY OF COMILATION AND RUNNING

    HelloWorld.java
        |
        | javac HelloWorld.java
        v
    HelloWorld.class
        |
        | java HelloWorld
        v
    (output)

------------------------------------------

** setting your CLASSPATH

   Q: Who can explain what the PATH does in Unix?

      note diff between : on linux and ; on Windows.

   CLASSPATH is similar, but used to find Java classes.

------------------------------------------
          THE CLASSPATH (ON LINUX)

On Linux, cygwin

  $ printenv CLASSPATH
  .:...
  $ java HelloWorld

What if "." is  not in the CLASSPATH?

  $ export CLASSPATH=""
  $ java HelloWorld

Using multiple directories:

  $ ls applogic userinterface
  $ cd applogic
  $ export \
  CLASSPATH="$HOME/classes/cs362/lectures/objects-classes/applogic"
  $ javac Message.java
  $ export \
  CLASSPATH=".:$HOME/classes/cs362/lectures/objects-classes/applogic"
  $ javac Message.java
  $ cd ../userinterface
  $ javac HelloWorld.java
  $ export \
  CLASSPATH="$HOME/classes/cs362/lectures/objects-classes/applogic"
  $ javac HelloWorld.java
  HelloWorld.java:6: cannot resolve symbol
  ...
------------------------------------------

     Q: So can you summarize how the CLASSPATH works so far?

** packages in Java

   change the package, and show what happens

------------------------------------------
                 PACKAGES

Goals:
   prevent name conflicts
   support large scale development

For each name N in package P
   can refer to N by P.N
   from outside package

Packages contain:
     classes, interfaces,
     packages

Example:

  userinterface
      HelloWorld
  applogic 
      Message
------------------------------------------

        Typical implementation is that each package is a directory
        on a file sys, but can also have packages stored in a database

------------------------------------------
          EXAMPLE

// Add the following line of code
// to put this class in package applogic.
package applogic;

/** This class knows the message to print.
 */
public class Message {

    /** the message */
    private String msg;

    /** Initialize this Message object. */
    public Message() {
        msg = "Hello, class!";
    }

    /** Return the message. */
    public String get() {
        return msg;
    }
}
------------------------------------------

        This example would have to be in a directory named applogic

        Q: What do we have to do to make the code in HelloWorld work
        with this?

             change the references to applogic or use import.

        compare to friends in C++

        Show how to compile this, and what changes are needed to
        CLASSPATH

        Q: Can you summarize how java and javac use CLASSPATH?

** Eclipse

------------------------------------------
        ECLIPSE EDITOR

Free, IDE for Java

Get it from:
    http://eclipse.org

Already installed on Linux:
    $ eclipse
------------------------------------------

   do the same stuff as above, under Eclipse

   Talk about views, perspectives, and editors

   Show how to manipulate projects:
        - open/close
        - adding libraries,
        - changing launch configurations