JRE : Java Glossary

Downloading the JRE

For Vista, make sure you are logged in as an administrator before you install. Some suggest it is best also to turn on UAC (that irritating Visa User Account control) during the install. The downloads are labeled as updates, but they are complete in themselves. You don’t need to install a previous version.

You might want to manually set your JAVA_HOME environment variable to the JRE directory e.g. C:\Program Files\java\jre6. Some software finds Java using this variable rather than poking around in the registry.

Polishing and Testing Your JRE

1. Configure your set environment for the CLASSPATH. If you are not sure use CLASSPATH=. See environment for details of how. See classpath for details.
2. Copy your various library jars into the C:\Program Files\java\jre6\lib\ext directory.Sooner or later you will have to reinstall the JDK/JRE and you will lose your ext directories. You can quickly rebuild them if you maintain a bat file like this and run it after every JRE/JDK install. Adjust the file to account for where your ext dirs are and where the jars are you need.
3. In Internet Explorer, go into Tools ⇒ Internet option ⇒ Advanced ⇒ Java(Sun). Make sure Sun Java is checked.
4. In Internet Explorer, make sure all three boxes under Tools Internet option ⇒ Advanced ⇒ Microsoft VM are checked.
5. In Internet Explorer 7+, you must OK allow blocked content permission to run Active X on the site, (even your own when running off-line). This also gives permission to run Java. Since Java is perfectly safe because it runs it a sandbox, logically it should not need special permission. This roadblock to Java is just part of Microsoft’s war on Sun and Java.
6. Test your JRE on the desktop by typing in a DOS box:

   java.exe -version

   You should see the expected version you just installed, probably 1.6.0. It can be problematic to have more than one version installed at a time.
7. Run Sun’s formal Applet test of the Java JRE in a browser.
8. Test your JRE browser’s ability to run Applets by running Sun’s
   Sun’s documentation on Sort demo
   .
9. Test your JRE browser’s ability to run signed Applets by running Wassup.

   It should tell you that your browser is using the JVM version you just installed, probably 1.6.0. Look for the line marked java.version. If Wassup does not run, or you have the wrong version, go into Settings ⇒ Control Panel ⇒ Java Plug-In ⇒ Browser and turn off each browser, then click apply, then turn them on again, then hit apply again. Then retest with Wassup. If that still does not work, turn on the Java console, try Wassup again and look for clues.

10. Test Java Web Start on the desktop by typing javaws.exe and running any sample application.
11. Check that the associations for the *.jnlp extension is set to point to the appropriate javaws.exe and *.jar is set to point to javaw.exe. Confirm this in any My Computer directory display with tools ⇒ folder options ⇒ file types.
12. Set up associations for *.jar files to make them double clickable, following the instructions here.
13. Check that Java Web Start is working in each browser by testing SetClock. Click SetClock to test.
14. Check the Opera browser’s quick preferences to make sure you have Java enabled. Turn on the console with tools ⇒ advanced ⇒ Java console to get some hints why it may not be working. Make sure Opera has *.jnlp files associated with mime type application-x-java-jnlp-file in preferences ⇒ files.
15. If you can’t get it to work, follow the failed install instructions.

Silent JRE Installs

Linux

Multiple JREs

Then instead of saying java.exe, use the fully qualified name to select which version of the java run time you want e.g. C:\Program Files\java\jre6\bin\java.exe.