You don't have any constructors in your vehicle class. That code from lines 46 to 48 in your post is a method named vehicle(), not a constructor. Remove the return type ("void") if you want to change it into a constructor.
One more thing: although your code is syntactically correct, it would help very much if you followed the code conventions which are generally used across the Java world. Following these standards, class names are capitalized: Vehicle, Car, and so on. Variable and method names start with lower-case letters and are "camel-cased" if they consist of more than one word: numberOfCars, driveHand, and so on. Almost everybody uses these conventions, to the extent that code which doesn't follow them (like the code you posted) is hard to read.