code: public static Constructor<?>[] constructorsDeclaredIn(final Class<?> cls, final Class<?>... additionalClasses) {
          if (cls == null) {
              throw new IllegalArgumentException("You need to supply at least one class.");
          }
          Set<Constructor<?>> constructors = new HashSet<Constructor<?>>();
          constructors.addAll(asList(WhiteboxImpl.getAllConstructors(cls)));
          for (Class<?> klass : additionalClasses) {
              constructors.addAll(asList(WhiteboxImpl.getAllConstructors(klass)));
          }
          return constructors.toArray(new Constructor[constructors.size()]);
      }
docs: Get all constructors in the supplied class(es).
  
  @param cls
  The class whose constructors to get.
  @param additionalClasses
  Additional classes whose constructors to get.
  @return All constructors declared in this class.