我已经配置好了环境变量了,javac编译能成功,生成class文件后用java命令运行的时候出错
Exception in thread "main" java.lang.NoClassDefFoundError: demo/class
Caused by: java.lang.ClassNotFoundException: demo.class
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
Could not find the main class: demo.class. Program will exit.
这是什么原因,连最简单的HelloWorld程序都无法运行
求高人解答