安装maven 中出现例如以下异常：
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/apache/ma
ven/cli/MavenCli : Unsupported major.minor version 51.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:14
1)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf(Cl
assRealm.java:401)
at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(
SelfFirstStrategy.java:42)
at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadCl
ass(ClassRealm.java:271)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm
.java:254)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm
.java:239)
at org.codehaus.plexus.classworlds.launcher.Launcher.getMainClass(Launch
er.java:144)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Laun
cher.java:266)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.jav
a:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(La
uncher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:
356)
出现如上异常 ： 由于之前jdk的版本号是 1.6 maven 版本号是 3.3 由于maven 3.3 jdk必须是 jdk7 所以从重装jdk 就可以