Do constructors always have to be public? [duplicate]

Answer 1

A constructor has to be at least protected or even private while creating, for example, custom factory classes, like:

public final class MyFactory {
  private MyFactory(){} // this one prevents instances of your factory
}

public static void doSomething(){} // access that with MyFactory.doSomething

Note that this is only one example showing when a constructor shouldn't be public.