Recently I upgraded Eclipse along with ADT plugins to Android L priew.
Eclipse
ADT plugin
Android L priew
I have the latest Java update as well i.e. Java 8
Java 8
You can see the following note in https://developer.android.com/preview/setup-sdk.html
Note: The Eclipse ADT plug-in requires Java 7 if your compilation target is the L developer preview.
Maybe you don't have Java 7 installed?