Maven error with Java 6 on OS X: “Unsupported major.minor version 51.0”

If you encounter the error below with Java 6 on OS X, make sure you’re using Maven 3.2.5 or older.

$ mvn
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/apache/maven/cli/MavenCli : Unsupported major.minor version 51.0
  at java.lang.ClassLoader.defineClass1(Native Method)
  at java.lang.ClassLoader.defineClassCond(ClassLoader.java:637)
  at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
  at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
  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(ClassRealm.java:401)
  at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:42)
  at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass(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(Launcher.java:144)
  at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:266)
  at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
  at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
  at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)

Maven error in OS X: “Maven already installed, it’s just not linked”

If you use Homebrew on OS X and you come across the error below, just:

  1. $ rm -rf /usr/local/Cellar/maven
  2. $ brew install maven
  3. $ mvn -version
  4. That’s it!

$ brew install maven
Updating Homebrew...
==> Auto-updated Homebrew!
Updated 2 taps (caskroom/cask, caskroom/versions).

Warning: maven-3.5.0 already installed, it's just not linked.