root@hadoopspark:~/share/mapreduce-demo# jar ./target/WordCountDemo.jar com.org.xidian.MapReduceWordCountDemo /input/input_file.txt /output Illegal option: . Usage: jar {ctxui}[vfmn0PMe] [jar-file] [manifest-file] [entry-point] [-C dir] files ... Options: -c create new archive -t list table of contents for archive -x extract named (or all) files from archive -u update existing archive -v generate verbose output on standard output -f specify archive file name -m include manifest information from specified manifest file -n perform Pack200 normalization after creating a new archive -e specify application entry point for stand-alone application bundled into an executable jar file -0 store only; use no ZIP compression -P preserve leading '/' (absolute path) and ".." (parent directory) components from file names -M do not create a manifest file for the entries -i generate index information for the specified jar files -C change to the specified directory and include the following file If any file is a directory then it is processed recursively. The manifest file name, the archive file name and the entry point name are specified in the same order as the 'm', 'f' and 'e' flags. Example 1: to archive two class files into an archive called classes.jar: jar cvf classes.jar Foo.class Bar.class Example 2: use an existing manifest file 'mymanifest' and archive all the files in the foo/ directory into 'classes.jar': jar cvfm classes.jar mymanifest -C foo/ .是为什么

这个错误是因为你在执行 `jar` 命令时，使用了一个不正确的选项 `.`。根据错误信息中的提示，正确的使用方式应该是 `jar cvf <jar-file> <source-files>`。其中，`cvf` 表示创建新的归档文件并显示详细输出，`<jar-file>` 是要创建的归档文件名，`<source-files>` 是要添加到归档文件中的源文件或目录。你需要将命令修改为类似这样的形式：

jar cvf WordCountDemo.jar com/org/xidian/*.class

其中，`WordCountDemo.jar` 是要创建的归档文件名，`com/org/xidian/*.class` 是要添加到归档文件中的源文件。另外，你需要确保当前工作目录为 `target` 目录，否则需要使用正确的路径来指定归档文件和源文件。