Gentoo's Bugzilla –
Attachment 391430 Details for
Bug 532258dev-java/netbeans-platform-8.0.2 with dev-java/oracle-jdk-bin:1.8 - .../work/nbbuild/templates/projectized.xml:96: You are attempting to build NetBeans using JDK 8 (or higher). This is forbidden as it may lead to accidental usage of JDK 8+ APIs.