Maven -- maven installation error: Exception in thread "main" java.lang.UnsupportedClassVersionError [duplicate]

Question

I've been trying to install and configure maven-3.3.3 for the past hour. When I type:

mvn --version

I get this error in cmd

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)

---

I've followed the official guide and also looked at several other blogs and forums.

Here are my system variables

JAVA_HOME = C:\Program Files\Java\jdk1.6.0_45
M2_HOME = C:\Program Files\Apache Software Foundation\apache-maven-3.3.3
MAVEN_OPTS = -Xms256m -Xmx512m

And I've added the following lines at the end of Path variable

%M2_HOME%\bin;%JAVA_HOME%\bin

Someone please tell me why I am getting this error. Thanks in advance.

---

P.S

java -version 

gives

java version "1.6.0_45"
Java(TM) SE Runtime Environment (build 1.6.0_45-b06)
Java HotSpot(TM) Client VM (build 20.45-b01, mixed mode, sharing)

Answer 1

You need to update to Java 7, as the class version 51.0 means, that it was built for Java 7. By the way, these are the valid versions:

J2SE 8   - 52
J2SE 7   - 51
J2SE 6.0 - 50
J2SE 5.0 - 49
JDK 1.4  - 48
JDK 1.3  - 47
JDK 1.2  - 46
JDK 1.1  - 45