Map a = Thread.getAllStackTraces();
for(Thread t : a.keySet()){
    if ("main".equals(t.getName())){
        StackTraceElement[] stack = t.getStackTrace ();
        StackTraceElement main = stack[stack.length - 1];
        String mainClass = main.getClassName ();
        System.out.println(mainClass);
    }
}

System.out.println(
    new Throwable().
        getStackTrace()[(new Throwable().getStackTrace()).length - 1].
        getClassName()
);