mvn -v 报 java.lang.NoClassDefFoundError异常

安装完成之后，运行mvn -v指令，发现出现异常。

Exception in thread "main" java.lang.NoClassDefFoundError: org/codehaus/classwor
lds/Launcher 
Caused by: java.lang.ClassNotFoundException: org.codehaus.classworlds.Launcher 
        at java.net.URLClassLoader$1.run(Unknown Source) 
        at java.security.AccessController.doPrivileged(Native Method) 
        at java.net.URLClassLoader.findClass(Unknown Source) 
        at java.lang.ClassLoader.loadClass(Unknown Source) 
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) 
        at java.lang.ClassLoader.loadClass(Unknown Source) 
        at java.lang.ClassLoader.loadClassInternal(Unknown Source) 
Could not find the main class: org.codehaus.classworlds.Launcher.  Program will 
exit.

出错原因:

  我环境变量里 M2_HOME  = d:\maven3

Path中设置 d:\maven2\bin

将Path中改为%M2_HOME%\BIN\

解决问题!