我已从https://jdk9.java.net/download/下载了jdk 9，并从http://openjdk.java.net/projects/jigsaw/quick-start#linkerJigsaw下载了快速入门指南，并根据本指南编写了第一个示例“Greetings”。该项目编译成功，但当我试图运行时，我得到了异常
E:\>java --module-path mods -m com.greetings/com.greetings.Main
Error occurred during initialization of VM
java.lang.module.ResolutionException: Error reading module: mods\com.greetings
at java.lang.module.Resolver.findWithBeforeFinder(java.base@9-ea/Unknown Source)
at java.lang.module.Resolver.resolveRequires(java.base@9-ea/Unknown Source)
at java.lang.module.Configuration.resolveRequiresAndUses(java.base@9-ea/Unknown Source)
at java.lang.module.ModuleDescriptor$1.resolveRequiresAndUses(java.base@9-ea/Unknown Source)
at jdk.internal.module.ModuleBootstrap.boot(java.base@9-ea/Unknown Source)
at java.lang.System.initPhase2(java.base@9-ea/Unknown Source)
Caused by: java.lang.module.InvalidModuleDescriptorException: Main.class found in in top-level directory (unnamed package not allowed in module)
at java.lang.module.ModuleInfo.invalidModuleDescriptor(java.base@9-ea/Unknown Source)
at java.lang.module.ModuleInfo.read(java.base@9-ea/Unknown Source)
at java.lang.module.ModuleDescriptor.read(java.base@9-ea/Unknown Source)
at java.lang.module.ModulePath.readExplodedModule(java.base@9-ea/Unknown Source)
at java.lang.module.ModulePath.readModule(java.base@9-ea/Unknown Source)
at java.lang.module.ModulePath.scanDirectory(java.base@9-ea/Unknown Source)
at java.lang.module.ModulePath.scan(java.base@9-ea/Unknown Source)
at java.lang.module.ModulePath.scanNextEntry(java.base@9-ea/Unknown Source)
at java.lang.module.ModulePath.find(java.base@9-ea/Unknown Source)
at java.lang.module.ModuleFinder$2.lambda$find$0(java.base@9-ea/Unknown Source)
at java.util.stream.ReferencePipeline$3$1.accept(java.base@9-ea/Unknown Source)
at java.util.AbstractList$RandomAccessSpliterator.tryAdvance(java.base@9-ea/Unknown Source)
at java.util.stream.ReferencePipeline.forEachWithCancel(java.base@9-ea/Unknown Source)
at java.util.stream.AbstractPipeline.copyIntoWithCancel(java.base@9-ea/Unknown Source)
at java.util.stream.AbstractPipeline.copyInto(java.base@9-ea/Unknown Source)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(java.base@9-ea/Unknown Source)
at java.util.stream.FindOps$FindOp.evaluateSequential(java.base@9-ea/Unknown Source)
at java.util.stream.AbstractPipeline.evaluate(java.base@9-ea/Unknown Source)
at java.util.stream.ReferencePipeline.findFirst(java.base@9-ea/Unknown Source)
at java.lang.module.ModuleFinder$2.find(java.base@9-ea/Unknown Source)
at java.lang.module.Resolver.findWithBeforeFinder(java.base@9-ea/Unknown Source)
at java.lang.module.Resolver.resolveRequires(java.base@9-ea/Unknown Source)
at java.lang.module.Configuration.resolveRequiresAndUses(java.base@9-ea/Unknown Source)
at java.lang.module.ModuleDescriptor$1.resolveRequiresAndUses(java.base@9-ea/Unknown Source)
at jdk.internal.module.ModuleBootstrap.boot(java.base@9-ea/Unknown Source)
at java.lang.System.initPhase2(java.base@9-ea/Unknown Source)
我找不到此异常的原因