Updating to Java 7

I've downloaded Java 7 binary blobs (jdk-7-linux-x64.tar.gz) from Oracle's website and installed it.

After installing the binaries, I added them [just java, not the rest yet] to alternatives running
either:

Code:

sudo update-alternatives --install /usr/bin/java java /usr/java/jdk1.7.0/bin/java 2000

or:

Code:

sudo update-alternatives --install /usr/bin/java java /usr/java/jdk1.7.0/jre/bin/java 2000

In doing so it becomes selected as default because it has the highest priority.

But when running (something valid like):

Code:

java -version

Code:

Error occurred during initialization of VM java/lang/NoClassDefFoundError: java/lang/Object

pops out.

Any ideas what's wrong?