All of the programs mentioned below are available for download on the Internet in the archive file: http://crack.seismo.unr.edu/ftp/pub/louie/class/757/java/jrg-src.jar. Make a ``jrg'' folder on your desktop and put the jar file in there. Unzip this archive with the following commands entered in a Terminal window:

cd desktop/jrg
unzip jrg-src.jar

1. Get Ready for Java: Make sure you are familiar with the computer you will use for the lab exercises in this course. To make changes to the Java-language programs that implement the exercises, you will need a Java Development Kit (JDK) version 1.1.3 or later. The code here is compatible as well with version 1.2 of the JDK, called the Java 2 Platform.

• The JDK can be found for any platform through java.com. It is free. Obtain it and install it on the machine you will use, if you do not have it already.

• Sun also offers documentation, and a tutorial.

• Geophysics past editor Bill Harlan explains how Java is useful in a Geophysical education.

• You will not need to learn very much about the Java language itself to complete the course exercises. While looking at a complete example, you will be asked to make small changes to the program. If you have ever programmed in Fortran, C, C++, Pascal, or even Basic, you should recognize enough of the program's syntax for you to proceed with the exercises.

  Do go through enough of the documentation supplied with the JDK so that you will know how to edit and compile applications, recognize compiler warnings and errors, and run your stand-alone Java applications on your computer. The exercises use stand-alone applications, and not ``applets'' that you would run from a Web browser.

• Click here for specific instructions on how to run Java applications on the Seismology Sun system.

• You will need a way to edit plain program text. There are commercial Java software development packages from Sun, Symantec, and many others that provide a fully integrated editing, re-compilation, and execution environment. For no cost, however, you can use the JDK and a basic text editor that comes with your computer's system software: WordPad on Windows; SimpleText on Mac; and vi, emacs, or textedit on UNIX. Any of these programs will read in a Java source code file (with a file name ending in .java), edit it, and save your changes before re-compiling the program.
  • WordPad on Windows 2000 introduces a new complication: whenever you Save your edited Java code, it appends a .txt to the file name. I could not find any way to remove this filename extension in the Windows 2000 Explorer, except the following procedure in a DOS window, for instance in editing looplet.java :

    del looplet.java (the file saved out of Wordpad is looplet.java.txt )
rename looplet.java.txt looplet.java

• It is most convenient if you can configure your web browser to show you the Java source code files right out of this web page, without having to save them to a file right away. The Seismology Sun server will deliver the .java files to you labeled as ``application/octet-stream'', and most web browsers will ask you what to do with the file. You can go to your browser's Preferences dialogs and look in the Navigator->Applications section, for example. Creat a new application type with Description: ``Java Program'', MIME Type: ``application/octet-stream'', and Suffixs: ``java''. Tell the browser to start a simple text editing application, as you should have selected above (on a UNIX browser, a command such as ``textedit %s'' will need to be entered). Click Apply or OK. Then test by clicking on this link to the looplet.java example program.

• The exercises ask you to print out and turn in some of your code alterations, and some of the plots that your Java applications make. Print code fragments from your text editing application. Use PrintScreen in Windows; the Mac's Command-Shift-3 snapshot method (drag Picture file into SimpleText, and print from there); or Sun's Snapshot application (or xv3 on UNIX) to capture graphical output. You can also select Write PostScript File... from the File menu of a plot window. The PostScript plot file you should be able to download or spool to a PostScript printer, or view and print from an application like Ghostview.

  In this class, it is also fine for you to email the PostScript plot files to the instructor. Please send a separate email message with each plot attached, giving the lab number and question number in the Subject line. Send the files to louie@seismo.unr.edu.

• More resources are available now from the Seismological Lab over the World-Wide Web. You should start ``Netscape'' from a Sun, Windows PC, or Mac on the network, and open the location ``http://crack.seismo.unr.edu''. From our home page you will be able to see the page for this course, and from the ``Lab People'' page you can find a list of suggestions for new staff. See also the notes on the RG and Seismic Unix processing systems, accessible from the ``Lab Resources'' page.

2. A Simple Example: Examine the Java-language program ``looplet.java''. The program would only be about ten lines long if it were not loaded with comments, meant to be a little tutorial in Java and object-oriented programming.

Copy looplet.java to a folder on your hard disk, where you will work on the code for the course exercises. On a Sun (in a CommandTool) or on a Windows95 PC (in a DOS window), you could compile and execute the stand-alone application with:

% javac looplet.java
% java loop

% "c:\Program Files\JavaSoft\JDK\1.2\bin\javac" looplet.java
% "c:\Program Files\JavaSoft\JDK\1.2\bin\java" loop

3. After a look at looplet.java, you should see that it also compiles into an Applet as well as a stand-alone application. The Applet code is looplet.class. A web page has been created that will allow you to view the Applet. It is called looplet.html. Click on the link to view the page and run the Applet.

4. Get JRG: At this point you should obtain the two Java Archive (.jar) files below, which contain all the files ending in ``.java'' and ``.class'', respectively. If you obtain just your own copy of the ``.java'' source code files you can use the javac compiler in the JDK to create all the ``.class'' files. The jar application that comes with the JDK will extract individual files from the achives:

• jrg-src.jar <200 kb of .java source code, compressed
• jrg.jar 500 kb of compiled .class files, not compressed

	jar xf jrg.jar

As an alternative, you can click on the FTP link to the Java code directory, and copy all the files there to your hard disk directory for the course. Make sure you use binary transfer mode for all files except the ones ending in ``.java'', the Java source code text files.

You may want as well the 4 Mb binary data file simult.ts file in the directory. You can then run the DixieSimultmod application (no compiling needed). You will need to have all the other .class files that form the course version of the JRG package in the same directory:

% java DixieSimultmod

5. Complex Arithmetic: Examine, compile, and run the application `` complextest.java''. You're right, Java does not handle complex numbers as neatly as FORTRAN. Change the program to print the result of dividing z2 by z1.

Complex multiplication and division are taken care of by the ``mul(z1, z2)'' etc. methods defined in the complextest class. Define a method (say, ``add(z1, z2)'') to add two complex numbers. Change the program to print z1+z2 as well. The JRG package has a class Complex with all these methods, that we will use frequently, but you can just use what is in complextest.java to polish up your memory of complex arithmetic.

6. List your directory and, if you like, browse through the Java programs set up for you. These are converted out of Claerbout's book, and will be used in later labs. The ``.java'' files beginning with small letters are the ones used in the class exercises; the ones starting with capitals are part of the JRG package that supports the exercises. The Web location for RG system documentation is `` http://crack.seismo.unr.edu/ftp/pub/louie/rg/rg.html''; the JRG package is under constant development.