Eclipse

Eclipse sometimes losing SDK in eclipse.ini. Mars requires at least v7 so it will fail to load with system default if you have only v6.

Resolve by adding this to eclipse.ini

-vm D:/dev/eclipse/java_1.7_64/bin/javaw.exe

Needs more investigation (maybe a config file update will fix).

install Java SE Development Kit (=JDK) http://www.oracle.com/technetwork/java/javase/downloads/index.html

The Java Development Kit (JDK) is an implementation of either one of the Java SE, Java EE or Java ME platforms. Oracle strongly suggests that they now use the term JDK to refer to the Java SE Development Kit. JDK (Java SE Development Kit) includes a complete JRE plus tools for developing.

Java Development Kit (JDK) 1.8 (officially named Java SE 8).

The Java EE SDK is available with or without the JDK, by which they specifically mean the Java SE 7 JDK.