IntelliJ: Error:java: error: release version 5 not supported

I’m using IntelliJ IDEA Ultimate 2019.3.1. Whenever I try to start any simple Java Maven project (may it be even a simple Hello World) I get the following error:

Error:java: error: release version 5 not supported

Running java --version by terminal I get the following output:

openjdk 11.0.5 2019-10-15
OpenJDK Runtime Environment (build 11.0.5+10-post-Ubuntu-0ubuntu1.1)
OpenJDK 64-Bit Server VM (build 11.0.5+10-post-Ubuntu-0ubuntu1.1, mixed mode, sharing)

Running javac --version by terminal I get the following output:

javac 11.0.5

Going to the Settings of the Java Compiler ( as suggested here ) I see this:

Java Compiler Settings

I tried editing the “Target bytecode version” to 1.8 but I get the following errors:

Error:(1, 26) java: package javafx.application does not exist
Error:(2, 20) java: package javafx.stage does not exist
Error:(4, 27) java: cannot find symbol
  symbol: class Application
Error:(12, 23) java: cannot find symbol
  symbol:   class Stage
  location: class Main
Error:(7, 9) java: cannot find symbol
  symbol:   method launch(java.lang.String[])
  location: class Main
Error:(11, 5) java: method does not override or implement a method from a supertype

Changing it to version 1.11 I get this error instead:

Error:java: Source option 5 is no longer supported. Use 6 or later.

What do you think is the problem? How may I solve it?

Answer

See https://stackoverflow.com/a/12900859/104891.

First of all, set the language level/release versions in pom.xml like that:

<properties>
  <maven.compiler.source>1.8</maven.compiler.source>
  <maven.compiler.target>1.8</maven.compiler.target>
</properties>

Maven sets the default to 1.5 otherwise. You will also need to include the maven-compiler-plugin if you haven’t already:

<dependency>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.8.1</version>
</dependency>

Also, try to change the Java version in each of these places:

File -> Project structure -> Project -> Project SDK -> 11.

File -> Project structure -> Project -> Project language level -> 11.

File -> Project structure -> Project -> Modules -> -> Sources –> 11

In project -> ctrl + alt + s -> Build, Execution, Deployment -> Compiler -> Java Compiler -> Project bytecode version -> 11

In project -> ctrl + alt + s -> Build, Execution, Deployment -> Compiler -> Java Compiler -> Module -> 1.11.