Java 小程序不可以执行

F:\江苏海院\专业文件\Java\java项目\新建文件夹>javac YuFa.java

F:\江苏海院\专业文件\Java\java项目\新建文件夹>java YuFa

Exception in thread "main" java.lang.NoClassDefFoundError: YuFa
Caused by: java.lang.ClassNotFoundException: YuFa
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: YuFa. Program will exit.

可以编译执行不起来，
跪求大神指导！