Solution:

① Check whether the package name contains “Java” and modify it. Java should be avoided when creating the package.

② Run the Java version and javac version commands in CMD to check their own JDK and JRE versions. If they are different, reconfigure the environment variables to make them consistent

The above two steps can solve most of the problems. If they are still not solved, it is recommended to reinstall the JDK and reconfigure the environment variables.