Gradle / IntelliJ IDEA: sourceCompatibility revert to previous value in IDE settings

Question

Setting sourceCompatibility and targetCompatibility to JavaVersion.VERSION_11 has not expected effect in my IntelliJ/Grade/Java project.

Even I set Project SDK and Project Language Level in Project Structure manually to 11, it reverted to 8 and 6 after I Refresh Gradle project (or Import Changes). See below image:

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To ensure I created a new project and test these in it. This is its tree view:

The only build.gradle file:

plugins {
    id 'java'
}

group 'test'
version '1.0-SNAPSHOT'

sourceCompatibility = JavaVersion.VERSION_11
targetCompatibility = JavaVersion.VERSION_11

repositories {
    mavenCentral()
}

dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
}

Gradle version is 4.10.2 as you can see it in gradle-wrapper.properties file:

#Tue Nov 13 00:53:45 IRST 2018
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.2-all.zip

And this is environment information:

IntelliJ IDEA 2018.1.5 (Community Edition)
Build #IC-181.5281.24, built on June 12, 2018
JRE: 1.8.0_152-release-1136-b39 amd64
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
Windows 10 10.0

This is an image from my SDKs:

---

Also, according to this answer, I made below configuration to build.gradle, but the problem persists:

group 'test'
version '1.0-SNAPSHOT'

allprojects {
    apply plugin: 'java'
    sourceCompatibility = JavaVersion.VERSION_11
    targetCompatibility = JavaVersion.VERSION_11
}

repositories {
    ...

And also below configuration according to another answer on the same post:

group 'test'
version '1.0-SNAPSHOT'

allprojects {
    apply plugin: 'java'

    tasks.withType(JavaCompile) {
        sourceCompatibility = JavaVersion.VERSION_11
        targetCompatibility = JavaVersion.VERSION_11
    }
}

repositories {
    ...

Answer 1

For such issues compatibility of tools matter, you can upgrade your IDE version to a version >= 2018.2.

Quoting a JetBrains blog #Java11 in IntelliJ IDEA 2018.2

The next version of Java is due out in September, and IntelliJ IDEA 2018.2 is ready for it.