Cannot get Java to work in Firefox

Solution 1:

It appears that the Java verification applet doesn't work with the implementation of Java that Ubuntu uses (OpenJDK), but other applets should work if you install the Java web plugin, which is a plugin that lets Java applets run in a web browser.

According to the community documentation for Java,

Browser plugin

1. Install the icedtea6-plugin package using any installation method.
2. Install the icedtea-7-plugin package using any installation method.

If you are using or want to use the default version of Java included with Ubuntu, just run

sudo apt-get install icedtea-plugin

If you want to use a specific version, just use the packages listed above.

Solution 2:

You need the browser plugin for Java to work in Firefox.

sudo apt-get install icedtea-plugin

Then sudo update-alternatives --config java

Check which version is activated: java -version

Install the icedtea-web plugin if not yet installed: sudo apt-get install icedtea-web