How to change project language level for all project in Intellij

Question

I am using Intellij. It is good, but when I create a new project or import a project the default project language level set to 6 (@override in interfaces). But I want to set

Answer 1

I changed the settings to Java 8 as advised above...->Default Project Structure.

It did'nt work!!

I continued not being able to write Lambda's in the editor without errors.

When I created the project, I chose Gradle as the build tool. For some reason my Java/Gradle project had the source compatibility in the build.gradle file set to 1.5 (maybe because my default was originally set to 1.5...I don't know as I did not bother to reproduce it):

apply plugin: 'java'

sourceCompatibility = 1.5

repositories {
    mavenCentral()
}

Changing the sourceCompatibility to 1.8 solved the problem, since the update to the gradle file also triggers a project build.

Word to the wise:

any newbie on Intelij should remember that not selecting either Maven or Gradle in conjunction with your Java project creation will not setup the default package (src/main/test and src/main/java) structures necessary; for eclipse users this is a real head scratcher when first starting to use Intelij.