This article describes and may help to resolve some specific issues related to Java. For general information on installing, enabling, and updating Java, see Using the Java plugin with Firefox.

Table Of Contents

• Java applet causes backwards or jumbled typing in text boxes
• Java Console disabled
• Java on Windows Vista
• Memory use
• Java applet causes Firefox process to remain in memory
• Java Plug-in for Netscape Navigator should not be used in Microsoft Internet Explorer
• Unable to change browser settings - Java Control Panel warning message
• Missing plugin alert even though Java is installed
• Error applying transforms. Verify that the specified transform paths are valid - Advanced
• Switching Java versions - Advanced

Java applet causes backwards or jumbled typing in text boxes

Sometimes running a Java applet during the browser session can cause the cursor to behave erratically when you type in a text field, so that your text will display backwards or jumbled. Additionally, you may not be able to copy text to the clipboard. If you are having these problems, exit Firefox completely (or restart the computer) and then reopen Firefox.

Java Console disabled

The JRE (Java Runtime Environment) installer includes a Java Console extension for Firefox (mainly for advanced users) that does not appear in the Add-ons window. The Java Console included with JRE 6.0 and JRE 6 Update 1 is not compatible with Firefox version 2.0.0.1 or later. If JRE 6.0 or JRE 6.0 Update 1 is installed, an "Incompatible Add-ons" dialog appears after you update to Firefox 2.0.0.1 or later versions, with a message that Java Console version 6.0 or 6.0.01 has been disabled. Java will still work in Firefox; only the Java Console add-on is disabled. You do not need to make any changes if you don't need the Java Console add-on. For more information on this issue, see Sun's bug report and this MozillaZine forum topic.

This issue is fixed in JRE 6 Update 2 so make sure you update to the latest version of Java. You will also need to uninstall the earlier Java 6.0 or Java 6.0 Update 1 version, to prevent future incompatibility messages (see this MozillaZine forum topic for more information).

Java on Windows Vista

If you are running Windows Vista on your system, one specific version of Java may cause the browser to hang. The reported Java version is build 1.6.0-oem-b104. For more information, see this MozillaZine forum topic.

To resolve the issue, download the latest version of the Java Runtime Environment (JRE) from Java.com and manually install it. According to this article, JRE 6 is the preferred version of Java for Windows Vista.

Memory use

All versions of Java can consume large amounts of memory, and JRE 5 versions may use substantially more memory than JRE 6. For more information, see this article.

If you are concerned about high memory usage, update Java to the latest available version.

Since plugins are not unloaded after use, restarting Firefox can also help. For more information, see the PluginDoc FAQ on memory usage.

Java applet causes Firefox process to remain in memory

When you close Firefox after running a Java applet, Firefox may remain in memory. When Firefox is restarted, a Close Firefox dialog may appear, including the following message:

To address this issue, try the following:

1. Allow the Java applet to fully load before closing Firefox.
2. Exit the page where the Java applet was loaded before closing Firefox. For example, click the Back button or visit a different web page before exiting Firefox.
3. Update to the latest version of Java.

Java Plug-in for Netscape Navigator should not be used in Microsoft Internet Explorer

If you receive the above error message when starting Firefox, the user agent string has been modified to a Microsoft Internet Explorer string. At start up, the Java plugin depends on the user agent string, and Sun does not support modified user agent strings.

To avoid this error message, you must revert to a user agent string that identifies a Mozilla browser.

• If you changed the user agent string using the User Agent Switcher extension, you should undo the change.
• If you made the change manually:

1. Terminate all Firefox processes by restarting the computer.
2. Open the Firefox profile folder. For the location, see the Profiles article.
3. Within the folder for the current profile, open the file prefs.js using a text editor such as Notepad.
4. Select and delete the line that begins with the following:
   user_pref("general.useragent.override
5. Save the file.

Unable to change browser settings - Java Control Panel warning message

If you are running on Windows, you may receive the following warning message:

You should disregard this warning if Java is otherwise working. This option is not relevant in this case.

The warning message may be caused by:

• Selecting Mozilla and Netscape for tag support in the Advanced settings of the Java Control Panel.
• Selecting Mozilla 1.1 and later in the Java Control Panel browser settings in Java 1.4.2 or earlier.

Missing plugin alert even though Java is installed

After you have successfully installed Java on your Windows machine, you may see a missing plugin alert or a symbol that looks like a puzzle-piece on pages containing Java applets. The issue is that you may be missing a registry entry that Firefox normally installs.

The solution is to re-install the latest version of Firefox, which also updates the Windows registry. For more information, see Installing Firefox on Windows.

Error applying transforms. Verify that the specified transform paths are valid - Advanced

If you receive the above error message when installing or updating Java, you should download the full offline Java installer. Close the browser and run the installer.

• The offline Java installer requires downloading the entire Java installation package, which is then installed from your local computer without contacting the download site over the Internet.

If the above error message appears again, do the following:

1. In the Windows Explorer menu, select Tools, followed by Folder Options....
2. Under the View tab, select Show hidden files and folders.
3. Click Apply to All Folders.
4. In your system's temporary application data folder, find the Sun\Java folder. For example:
   • (Windows XP) C:\Documents and Settings\<username>\Local Settings\Application Data\Sun\Java
   • (Windows Vista) C:\Users\<username>\AppData\Local\Sun\Java
     where <username> corresponds to the username you used to login to Windows.
5. Inside the Java folder, find the folder that corresponds to the installed version of Java. For Java 6.0 Update 1, the folder is jre1.6.0_01.
6. Open the folder.
7. Run the MSI file inside this folder to complete the installation.
8. You may wish to revert the setting that displays hidden files at this time.

• Additional detail on this topic can be found here.
• For more information on this topic, see the Sun Microsystems forum.

Switching Java versions - Advanced

If multiple Java versions are installed on your computer, the latest version is normally used, and Firefox can find the Java plugins via plugin scanning.

To verify that the plugins are being detected, enter about:plugins in the Firefox Location bar. In the displayed page, verify that the appropriate plugins are being used.

To switch to an earlier Java version in Firefox without uninstalling other versions, you must disable plugin scanning and copy the plugins to use into the Firefox plugins folder:

1. To disable plugin scanning, enter about:config in the Firefox Location bar.
2. Find the preference plugin.scan.SunJRE. Change its value to 9.9. This value represents the minimum version of Java for plugins detected during plugin scanning to be loaded. Since no plugins have been created for Java 9.9, plugin scanning is effectively disabled.
   • You must perform the above edit on each Firefox profile that you use.
3. Close Firefox.
4. Copy the plugins you want to use. Copy the np*.dll plugin files from the Java installation folder of the version you wish to use to the Firefox plugins folder.
5. Copy these files into the Firefox plugins folder. Typically, this folder is located here:
   C:\Program Files\Mozilla Firefox\plugins.
6. When you restart Firefox, the Java plugins you copied to the plugins folder are used.

Note: If you no longer want to use the earlier version of Java in Firefox, reset the plugin.scan.SunJRE Java version preference and remove the Java plugin files from the Firefox plugins folder.