How to set new JDK home in NetBeans IDE after Java update (NetBeans IDE refuses to start)

To find the variable which sets the JDK home for Netbeans you need to open the config file which sets it (replace <versionNumber> with the version number of your NetBeans, such as 8.0.2 and make sure that you are in the directory which the NetBeans folder is in, this will most likely be your home directory, to cd to that do: cd ~):

gedit netbeans-<versionNumber>/etc/netbeans.conf

And then locate variable called netbeans_jdkhome and set it to the current location of your JDK folder. For example it could look something like this (<username> replaced with your username):

netbeans_jdkhome="/home/<username>/jdk1.8.0_40"

Then save your changes to the config file, and NetBeans should launch with no problem.