If We Dont Have Costrutor To subclass,
java implicitly create One no arg construtor. (i.e. default Costructor) This Constructor Has A Call To The default Constuctor Of Super Class. As Java provides implicit constuctor Only for those classes who dont have Any Constructor.
Hence to Avoid All Of default Constuctor Of Super Class We Must Have An Explict Constuctor For subclass To call Predefined parametric constuctor of super class.