IntelliJ IDEA 2016.1(64) : Unsupported java version Cannot start under Java 1.7.0_79-b15: Java 1.8 or later is required

You should create IDEA_JDK_64 environment variable and set its value to JDK8 instance location on your computer.

This JDK8 instance can be used only for idea and JAVA_HOME can point to the Java 7 at the same time without any problems.

Via documentation:

idea64.exe uses this JDK search sequence:

• IDEA_JDK_64 environment variable
• ..\jre64 directory
• system Registry
• JDK_HOME environment variable
• JAVA_HOME environment variable