How to make Firefox use the newest Java version, which is already installed?

Apparently, I have OpenJDK 6 JRE (openjdk-6-jre 6b27-1.12.6-1ubuntu0.12.04.2) and 7 JRE (openjdk-7-jre 7u25-2.3.10-1ubuntu0.12.04.2) installed in parallel – I don't know why I have both of them, I can't remember installing any of them manually.

However, the Firefox Java plugin is occasionally reported to be out of date by some websites, and it seems to me that it relies on JRE 6. How can I make Firefox use the newer version? Removing JRE 6 seems like a bad idea; when I attempted to do so in synaptic it appeared to me that a lot of software still relies on the older JRE, since removing it would have removed programs like jedit as well.

Do I mix up stuff? I'm not even sure how the FF plugin interferes with the OpenJDK JRE's.

EDIT:

Having tried even more, the problem persists. Using update-alternatives --config java, I see that the default Java version (with status "manual mode") is already set to Java 7, and java -version returns "1.7.0_25". The file /usr/lib/jvm/java-7-openjdk-i386/jre/lib/i386/IcedTeaPlugin.so exists, but still Firefox shows the Java 6 plugin when looking at about:plugins.

To sum it up:

How do I make Firefox use the IcedTea plugin belonging to the default Java version?

Solution 1:

Install the version 7 of the icedtea plugin either from the software center or using command line:

Open a terminal by pressing Ctrl+Alt+T and enter:

sudo apt-get install icedtea-7-plugin

Remove the older icedtea:

sudo apt-get remove icedtea-6-plugin

Then restart Firefox and type about:plugins to check the version of java plugin. Or go to java website to check the version as well as if it is working properly.

Hope this helps

Solution 2:

Most of those websites are using javascript to check what version of Java your browser is running and since it does not match the Oracle Java version they complain that you need to update Java in your system. I would ignore any of those messages if the Java applets are working properly.

To check what version of Java Firefox is running just type on the location bar (address bar) about:plugins, it should display all the plugins Firefox is using.

I bet Firefox is using the latest JRE and the websites are just complaining that it is not the same version as Oracle is. Keep your system updated and ignore that.

Solution 3:

If you're using Fedora you need to install

sudo yum install icedtea-web

Restart your browser after this.