Error: Could not find or load main class org.codehaus.plexus.classworlds.launcher.Launcher
You mentioned M2_HOME environment variable incorrectly.M2_HOME environment variable should be "/home/mani/apache-maven-3.2.5"
export M2_HOME=/home/mani/apache-maven-3.2.5
and Add the $M2_HOME/bin directory to your path.