[FIXED] IntelliJ - Invalid source release: 17

Issue

I've created a new Java project in IntelliJ with Gradle that uses Java 17. When running my app it has the error Cause: error: invalid source release: 17.

My Settings

I've installed openjdk-17 through IntelliJ and set it as my Project SDK.

The Project language level has been set to 17 - Sealed types, always-strict floating-point semantics.

In Modules -> Sources I've set the Language level to Project default (17 - Sealed types, always strict floating-point semantics).

In Modules -> Dependencies I've set the Module SDK to Project SDK openjdk-17.

In Settings -> Build, Execution, Deployment -> Compiler -> Java Compiler I've set the Project bytecode version to 17.

Gradle

plugins {
    id 'org.springframework.boot' version '2.5.6'
    id 'io.spring.dependency-management' version '1.0.11.RELEASE'
    id 'java'
}

group = 'com.app'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'

repositories {
    mavenCentral()
}

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-websocket'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
    implementation 'com.fasterxml.jackson.core:jackson-core:2.13.0'
    implementation 'com.fasterxml.jackson.core:jackson-databind:2.13.0'
}

test {
    useJUnitPlatform()
}

I've looked at all of the answers here but I can't seem to fix this. I must be missing something but I can't find it. I've not had any problems using Java 8 or 11.

How do I resolve this?

Solution

The message typically entails that your JAVA_HOME environment variable points to a different Java version.

Here are the steps to follow:

• Close IntelliJ IDEA
• Open a terminal window and check your JAVA_HOME variable value:
  • *nix system: echo $JAVA_HOME
  • Windows system: echo %JAVA_HOME%
• The JAVA_HOME path should be pointing to a different path, then set it to the openjdk-17 path:
  • *nix system: export JAVA_HOME=/path/to/openjdk-17
  • Windows system: set JAVA_HOME=path\to\openjdk-17
• Open your project again in IntelliJ IDEA
• Make sure to set both source and target compatibility versions (not only the sourceCompatibility)

You should be able to build your project.

EDIT: Gradle Toolchain

You may need also to instruct Gradle to use a different JVM than the one it uses itself by setting the Java plugin toolchain to your target version:

// build.gradle
java {
    toolchain {
        languageVersion = JavaLanguageVersion.of(17)
    }
}

Answered By - tmarwen
Answer Checked By - Marilyn (JavaFixing Volunteer)