Where a nonconforming use is changed to a use permitted in the district in which it is located, it shall not thereafter be changed from said conforming use to a nonconforming use.

Whenever there shall be a discontinuance or cessation of any nonconforming use for a period of one year, such nonconforming use shall be adjudged as abandoned, and the premises can only thereafter be used in conformity with the existing requirements of the zone or district in which said premises are located.