Tips & Techniques - Java - April 1996

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By IBM

Tip
On an OS/2 command line, Java programs should be started with the "java" executable; Java programs that use AWT windows should be started with the "javapm" executable.
Tip
View Java ouput written to standard out and standard error by piping both stdout and stderr to a file.
Tip
Make sure that you install the JDK 1.0 for OS/2 on an HPFS partition; we're working to make the runtime FAT compatible.
Tip
View Java applets under the JDK 1.0 for OS/2 using the "applet" executable, rather than "appletviewer" as on some other platforms.
The applet viewer automatically redirects stdout and stderr output to a weblog file in the x:\javaos2\weblogs directory
Tip
Run several applets simultaneously without receiving an error from the "appletviewer."
Technique
Imbed several applets in a single HTML document, using the applet tag, and open that document using "applet 'http://path/document.html'", you should see multiple applet viewer windows open. All should run fine.
Tip
Use environment variables to modify the behaviour of the Java runtime.
Technique
Set environment variables as follows:
JAVA_CONNECT_TIMEOUT=n will adjust the time that Java will wait for a network connection before reporting a timeout. 'n' is in seconds, from 1 through to a million (default = 30).
JAVA_AUDIO_VOLUME=v will adjust the volume that Java will use for audio output and is a percentage of the maximum volume. 'v' may take a value from 0 to 100 (default=75).
JAVA_AUDIO_RATE=n will set the preferred playback sample rate for audio. A value for 'n' of 8 will replay at 8000 per second, or 11 for 11025 samples per second. The Java runtime will normally try 8000 first (to match the incoming data stream) and then 11025; some drivers (notably some ThinkPad 701C early drivers prior to October 1995) appear to support 8000 but then fail; they can be made to work by forcing the playback rate to 11025.
JAVA_HOME=<dir> will set the path to the shared Java runtime directories.
JAVA_USER=<dir> will set the path to the directory into which and from which user specific files will be accessed, eg .hotjava\properties file.
JAVA_WEBLOGS=<dir> will set the path to the directory into which the Java runtime will write weblog files for each started Java process.
Tip
Set up your standalone machine to do local testing of your Java application.
Technique
Perform the following:
  1. Install either the Internet Access Kit from the OS/2 Warp BonusPack or TCP/IP 3.0 from OS/2 Warp Connect.
  2. Specify SET USE_HOSTS_FIRST=1 in your CONFIG.SYS file.
  3. Create a file called "hosts" in your \ETC directory. The easiest way to do this is to " E %ETC%\hosts". In this file, place the following line:
    127.0.0.1 here (where 127.0.0.1 here is the hostname)
  4. After TCPSTART.CMD has executed, execute the following command:
    ifconfig lo 127.0.0.1
    • Note: This establishes a "loopback" device that will allow your machine to talk to itself. If you install TCP/IP 3.0, the parallel port NDIS driver that it installs also loops back if you don't have a laplink cable installed.
  5. Test using 127.0.0.1 as the IP address or whatever host name you specified in the "hosts" file.

Reprint Courtesy of International Business Machines Corporation, © International Business Machines Corporation