SDSU CS 696 Emerging Technologies: Distributed Objects
Spring Semester, 1998
Java on Rohan - Corrected

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© 1998, All Rights Reserved, SDSU & Roger Whitney
San Diego State University -- This page last updated 21-Apr-98

Contents of Doc 2, Java on Rohan - Corrected

  1. References
  2. Some Java Information
    1. Java on Rohan
      1. Classpath
    2. SDSU Java Library
    3. Packages
    4. Javadoc


Javadoc documentation at:

FixJavadoc documentation at:

Rohan system administrator

The Java Programming Language, Arnold, Gosling, 1996

Doc 2, Java on Rohan - Corrected Slide # 2

Some Java Information

Java on Rohan

Version of Java available:

JDK 1.0.2
Compatible with Netscape 3.0 browsers
For applets

JDK 1.1.3
Last semester this was the only version of java that would run an application that used a GUI (awt) and display it on the NCD terminals in the campus labs
JDK 1.1.5
Current release of Java

JDK 1.2b2
Second beta version of the next major release of Java
API is at least twice the size of the 1.1.x API
Default Version

/opt/java points to the current "safe" version of java on rohan

Doc 2, Java on Rohan - Corrected Slide # 3
Java GUI Applications & NCD Terminals

There is problem running a java GUI based application on the NCD terminals on campus

The problem is with the old version of the NCD software (3.x) running on the NCD terminals

Reports are that version 5 of the NCD software fixes the problem, however NCD does not support the version of the terminals in BAM and in E301. A few terminal in the library can run version 5

This does not affect applets running in a browser, but does affect applets running in the appletviewer

You must type
   xstdcmap -all" 

at the shell prompt before you run a java application that uses AWT and have it display on an NCD X-terminal in the BAM labs

This does not work with some window managers like fvwm

In JDK 1.1.5 and 1.2b2 the window coordinate system on the NCD is off by 10-30 pixels
You need add 10-30 pixels to the y coordinate system so that the top of the window is accessible

Doc 2, Java on Rohan - Corrected Slide # 4
Using a Version of Java

Add to your path the location of the java bin directory of the version you wish to use
Current version/opt/java/bin

As new versions of Java are released older versions of the JDK will be removed from Rohan

If you hard code in your path a particular jdk, when it is removed, you will have to modify your path

/opt/java was created to allow users to avoid having to change their environments each time a new version of jdk is released

You can use a version of java not on your path by explicitly referencing it in the command line:

/opt/jdk1.2beta2/bin/java     foo

If you do this a lot alias the command

Doc 2, Java on Rohan - Corrected Slide # 5


Set the CLASSPATH environment variable to point to locations that contain java packages that you with to use

There is no need to include the location of the standard Java packages, it is done for you by java

The following classpath will access classes in the current directory, the SDSU Java library, and all the Java API of the version of java you are running

setenv CLASSPATH  '.:/usr/local/lib/java'

I use the following classpath to access Java classes in my home directory
setenv CLASSPATH  '.:/usr/local/lib/java:/home/ma/whitney/java/classes'

Currently there are some problems using the file in /usr/local/lib/java, so it is better to use the classpath given above

Note /opt/local and /usr/local are refer to the same directory on Rohan

Doc 2, Java on Rohan - Corrected Slide # 6

SDSU Java Library

The SDSU Java library contains ~100 classes, some of which may be useful in your assignments

The library is on Rohan, Moria and is free

Documentation is at:>

You can also download the library from that URL

Doc 2, Java on Rohan - Corrected Slide # 7


Each class belongs to a "package"

A package creates a name space

A package defines the full name of a class

Standard packages
java.applet java.awt.peer
java.awt java.util
java.awt.image java.lang

Example - PrintStream

PrintStream is in the package

The full name of the class is
class Output {

   public static void main( String args[] ) {  myOut  =  System.out;
      myOut.print(  "Look Mom, No System.out" );

Doc 2, Java on Rohan - Corrected Slide # 8
Import Statement

The import statement allows you to shorten class names

class Output {

   public static void main( String args[] ) {
      PrintStream  myOut  =  System.out;
      myOut.print(  "Look Mom, No System" );


class Output {

   public static void main( String args[] ) {
      PrintStream  myOut  =  System.out;
      myOut.print(  "Look Mom, No System" );

Default Import

All classes in the java.lang are imported in all programs by default

Doc 2, Java on Rohan - Corrected Slide # 9
Placing a class in a package
package  sdsu.roger;

public  class  Sample  {
   public  void  hello()  {
      System.out.println( "Hello for package sdsu.roger" );

Place program in file named ""

Place file "" in directory called "roger"

Place directory "roger" in directory called "sdsu"

Place directory "sdsu" in "~whitney/java/classes"
Placing classes in a directory called classes is just a convention that I use, it is not required

Make sure that "~whitney/java/classes" in the CLASSPATH environment variable
Place the following class anywhere you like and compile
import  sdsu.roger.Sample;

class TestPackage {

   public static void main( String args[] ) {
      Sample  me  =  new  Sample();

Doc 2, Java on Rohan - Corrected Slide # 10
Class Access Levels

Accessible to code in and outside a package

Accessible to code in package only
No subclasses outside package
package Botany;

public class Leaf
   public Leaf()
      System.out.println( "Leaf in a real tree" );

package Botany;

class BotanyHelper
   // Only code in package Botany can use this class

Doc 2, Java on Rohan - Corrected Slide # 11
Package Notes

If a class has no declared package, it is in the unnamed package

CLASSPATH needs to point to the root directory containing the binaries of packages

There is no requirement to have both binaries and source code of a package in the same location.

Doc 2, Java on Rohan - Corrected Slide # 12


Using Javadoc

There are three steps in creating java documentation using javadoc. First there is inserting the proper comments in your source code. Second is running javadoc. Third is modifying the output of javadoc to properly find the standard images use in javadoc documentation.
Javadoc Comments

Comments that start with /** and end with */ that are placed just before methods, constructors, fields, classes, and interfaces are used by javadoc to generate javadoc documentation. The following small example illustrates some javadoc comments. See for more details on javadoc comments and the javadoc tags.

Doc 2, Java on Rohan - Corrected Slide # 13
Sample Program with Javadoc tags
package cs535;
 * This is a javadoc comment for the entire class. Below I
 * use some special tags.
 * @version 0.1 28 November 1997 
 * @author Roger Whitney 
 *   (<a></a>)
 * @see
 * @see java.util.Vector
public class SampleClass
    * This is a javadoc comment for a field.
   private int myField;

      This is a javadoc comment for a method. Note that
      I don't need to use the line of *'s at the left.
     @param right Describe right here.
     @param left Describe left here.
     @exception IOException Talk about the exception here.
     @return a float value is returned
   public float test( int  left, int right ) throws IOException
      return 5.0f;

Doc 2, Java on Rohan - Corrected Slide # 14
Running Javadoc

See for the "official" documentation on javadoc with all the flag options. The most common mistake beginners make it javadoc is not making their classes public. Javadoc does not produce documentation for non-public classes. Another common mistake is not using the proper flags to display all the javadoc tags in your classes. Not all tags are displayed by default. The general format of the javadoc command line is:

javadoc [options] packages or files to process

For example I put the above program in a file in the directory /net/www/www eli/java/cs535. I then moved to the directory /net/www/www eli/java. I then ran the following command:

javadoc -version -author -d myDocs cs535

The -version -author flags tell javadoc to show the version and author tags. The -d myDocs flag tells javadoc to place the html documentation in the directory myDocs. This directory must exist before you run the command. The path cs535 tells javadoc to process all .java files in the subdirectory cs535. You can give relative or absolute path name. You can also give a path to the top level of a package to have javadoc generate documentation for all classes in a package. The contents of myDocs is now:
AllNames.html   cs535.SampleClass.html   tree.html
Package-cs535.html   packages.html

The following command done in the directory /net/www/www-eli/java/cs535 (which contains the file will generate the javadoc documentation for all files ending in .java in the current directory.

javadoc *.java

Doc 2, Java on Rohan - Corrected Slide # 15
Modifying Javadoc output

Javadoc has one irritating feature: it assumes that all images used in the javadoc html documentation are in a subdirectory of the directory containing the javadoc documentation. When you view this documentation with a web browser you will see boxes there the images for methods, constructors, fields, etc., should be located. There are two ways to correct this. The first one is to copy the directory of images to the directory containing your javadoc documentation. The second way is modify the html files to reference a local where the images are actually located.


The Java class sdsu.doc.FixJavadoc modifies .html files so that the images are referenced from a valid location over the network. To modify all .html files in the current directory use the command:
   java  sdsu.doc.FixJavadoc


for more details and options.

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