Java Troubleshooting

On cal-mum.com we use JavaScript and Java Applets for numerous server functions to give the site a better appearance. Java is a programming language promoted by Sun Microsystems. When it comes to deploying programs on the Internet, Java has numerous advantages over traditional languages such as Visual Basic, C, and C++. Two significant advantages of Java are:

• Java programs are much smaller (meaning they download quickly).
• Java can run on almost all computers and operating systems (e.g., Linux, Mac, Solaris, Windows, etc.).

This page will help you troubleshoot problems running Java applets in your browser. 

Test Applets

A gray, rectangular Java applet should be displayed below this paragraph (it may take a minute or two for the applet to appear). This applet tests your browser's ability to run a Java version 1.0 applet. If the gray rectangle is not displayed, if the rectangle is displayed but it does not contain several lines of text, or if the words "Your browser is unable to run Java version 1.0" are displayed, your browser or Internet provider does not support Java applets. Scroll down this page for additional information.

Your browser is unable to run Java version 1.0

A gray, rectangular Java applet should also be displayed below this paragraph (it may take a minute or two for the applet to appear). This applet tests your browser's ability to run a Java version 1.1 applet from a jar file. If the gray rectangle is not displayed, if the rectangle is displayed but it does not contain several lines of text, or if the words "Your browser is unable to run Java version 1.1" are displayed, your browser or Internet provider does not support Java 1.1 applets. Scroll down this page for additional information.

Your browser is unable to run Java version 1.1

Interpreting the Test Results

If both of the above applets displayed correctly:

• Your browser is correctly configured to run Java applets.

If only the first of the above applets displayed correctly:

• Your browser supports Java version 1.0, but not version 1.1 applets.

If neither of the above applets displayed correctly, either:

• Your browser does not support Java.
• Your Internet provider's firewall (or proxy) is blocking Java applets.
• Your browser is configured to block Java applets (unlikely).

General Problem Solving

If you suspect your browser does not support Java (or if it only supports Java version 1.0), follow these links to download the most recent version of either the Microsoft Internet Explorer or the Netscape Navigator (contained within the Netscape Communicator).

If you suspect your Internet provider is blocking Java applets with a firewall or proxy (this is very common if you access the Internet from your office network, and not very common with commercial ISPs), ask your system administrator if this is the case and if so, ask if they'll change it. System administrators often block Java applets as a security precaution as they don't understand that Java applets are extremely safe and cannot modify anything on your computer.

If you suspect your browser is configured to block Java applets, some browsers do have a "disable Java" option.  You can access this setting in version 5.x of the Microsoft Internet Explorer by choosing “Tools | Internet Options | Security | Internet | Custom Level | Java” (in version 4.x, choose “View | Internet Options | Security | Custom | Settings | Java”),  This should not be set to "Disable Java"

The Java Console

You can often learn why you are unable to run Java applets by displaying the Java Console from within your browser and then attempting to run a Java applet. The Java Console may display messages informing you that the Java applet was not found, that it caused an error (an 'Exception'), that it was blocked by a firewall, etc.

Displaying the Java Console from the Microsoft Internet Explorer

• Choose View on the main menu and then choose Java Console.
  
  If there is not a Java Console choice in the View menu:
• In version 5.x, choose Tools on the main menu and then choose Internet Options. In version 4.x, choose View on the main menu and then choose Internet Options.
• Click on the Advanced tab in the Internet Options dialog.
• Use the scrollbar to scroll down the list to the Java VM section.
• Make sure the Java console enabled checkbox contains a check.
• Exit and restart the Internet Explorer.
• Choose View on the main menu, and then choose Java Console.

Displaying the Java Console from the Netscape Navigator

• Choose Communicator on the main menu.
• Choose Tools and then Java Console from the Tools submenu.

Specific Java Console Messages

The following are a few of the numerous error messages that can appear in the Java Console.

• If a message similar to "java.lang.NoSuchMethodError: java.awt.TextArea" is displayed, you probably need to upgrade your browser.
• If a message similar to "Cannot find class java/awt/event/ActionListener" is displayed, you probably need to upgrade your browser.
• If a message containing the term "FileNotFoundException" is displayed, it probably means either (1) you need to upgrade your browser (i.e., the browser doesn't support jar files, so it can't find the init() class) or (2) something is missing on the server (i.e., the developer of the applet forgot to put an important file on the server).

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