IntelliJ IDEA 13 uses Java 1.5 despite setting to 1.7

Question

Despite specifying JDK 1.7 in all project settings (including in File -> Project Structure -> Project :: Project SDK), the following error is produced by

Answer 1

In your command line(Unix terminal) Go to your project root folder, and do this

find . -type f -name '*.iml' -exec sed -i '' s/JDK_1_5/JDK_1_8/g {} +

This will change the language level property in all your project .iml files from java 1.5 to java 1.8.