VSCode Unbound classpath container JRE System Library [JavaSE-15]

I have been programming a java project using JDK14 and VSCode. Recently JDK15 is available, and I switched to the JDK. As for configuration, I pointed the VScode java.home and system JAVA_HOME to the new JDK folder.

When I clear the VSCode cache and restart the IDE, I started receiving this error

{
"resource": "/E:/dev/java/challenges/",
"owner": "_generated_diagnostic_collection_name_#3",
"code": "963",
"severity": 8,
"message": "Unbound classpath container: 'JRE System Library [JavaSE-15]' in project 'challenges'",
"source": "Java",
"startLineNumber": 1,
"startColumn": 1,
"endLineNumber": 1,
"endColumn": 1
} 

I have seen similar questions/answers, but none of them was directed to VSCode.

https://stackoverflow.com/a/42525941/1005462
this one was helpfull;

replace :
build block in POM to

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
    </plugins>
</build>

According to VsCode-Java in Twitter, JDK15 support won't be released until the end of September, and here is a github issue that's related to Java 15 not support.

I am new to building Java apps in VSCode. In my case, I was developing a microservice using Spring Boot. Here is what I've done to solve the issue ;

1. Make sure JAVA_HOME env variable is registered to the right path
2. Configured JDK path in java.jdt.ls.java.home to settings.json located inside .vscode. Here is my configuration.
   <pre>
   {
   "java.configuration.updateBuildConfiguration": "automatic",
   "java.compile.nullAnalysis.mode": "automatic",
   "java.jdt.ls.java.home": "/Library/Java/JavaVirtualMachines/temurin-11.jdk/Contents/Home"
   }
   </pre>
3. Restart the VSCode