Oracle's Java 1.8 appears to not actually install itself
Run the installer again, but open the Installer Log window by choosing "Installer Log" from the Window menu or hitting cmd ⌘+L. This might help you discover if the installer is having a problem when it is trying to install Java 1.8 on your system. By default it is set to "Show Errors Only" but you can see more detail by changing it to "Show All Logs" from the drop-down in the top-left corner of the Log window.



Another way to see exactly what is happening when you are installing Java 1.8 is to use the following command in a Terminal window, replacing PATHTOINSTALLPACKAGE with the location of the "JDK 8 Update 45.pkg" file. The easy way to do this is to type (or copy and paste) the first part of the command up to "-pkg " and then drag and drop the PKG file (the one with the yellow cube emerging form the brown box icon) onto the Terminal window.

 sudo installer -verboseR -target / -pkg PATHTOINSTALLPACKAGE


So you should end up with something like this.

 sudo installer -verboseR -target / -pkg /Volumes/JDK\ 8\ Update\ 45/JDK\ 8\ Update\ 45.pkg


Then hit ENTER and enter your password.

You should get output that tells you exactly what is happening.

installer:PHASE:Preparing for installation…
installer:PHASE:Preparing the disk…
installer:PHASE:Preparing JDK 8 Update 45…
installer:PHASE:Waiting for other installations to complete…
installer:PHASE:Configuring the installation…
installer:STATUS:
installer:%5.810995
installer:PHASE:Writing files…
installer:%7.044070
installer:PHASE:Writing files…
...
...
...
installer:%79.565404
installer:PHASE:Moving items into place…
installer:%80.175556
installer:PHASE:Moving items into place…
...
...
...
installer:PHASE:Running package scripts…
installer:PHASE:Running package scripts…
...
...
...
installer:PHASE:Validating packages…
installer:%97.750000
installer:STATUS:Running installer actions…
installer:STATUS:
installer:PHASE:Finishing the Installation…
installer:STATUS:
installer:%100.000000
installer:PHASE:The software was successfully installed.
installer: The upgrade was successful.


If it is failing at some point it should tell you. Let us know how you get on.