I\'m using IntelliJ IDEA Ultimate 2016.2.1, have set Project SDK to my 1.8 version, Project Language Level to 8, Module SDK to my 1.8 version, and JDK home path to /Library/Java
I have found that IntelliJ sometimes defaults modules to language levels that don't match the set project SDK. Try right clicking on the module in the project explorer and select module settings and then the language level tab. If that is set to Java 5 then update it to Java 8.