--list-modules, --validate-modules and --describe-module options are terminal options. It exits after it does its job and prints the result.

java --list-modules -m abc
   - This uses the specified initial module as the root for the module resolution.

java --validate-modules -m abc
   --validate-modules ignores -m and any modules specified via --add-modules. It only resolves all system modules.

Other launcher terminal options include -version, -jar, and --module.

java -version -m abc
   - all arguments following -version is ignored.

java --validate-modules --list-modules
java --list-modules --validate-modules
   the current behavior accepts both terminal options but always list modules and exit. I think we should reject when both options are specified. Similarly, -m can't be combined with these options and maybe when any argument following --list-modules, --validate-module, --describe-module <module-name> is specified.