Question

I’m novice to java and learning my way through it.
Is it necessary to have a argument constructor for superclass if subclass have argument constructor, what happens if subclass have argument constructor and superclass have default no-argument constructor?

Answer 1

It would not be a problem – but you can explicitly invoke super() in the constructor of the subclass (as the first statement in the subclass’ constructor), or let the compiler do it for you – as it implicitly invokes an argmentless constructor (if one exists) as the first step.

Doing one of these will “let the class know” how to build the super class.

Example:

class A { 
//defaulut argumentless constructor is implicitly created
}

class B extends A {
  B(int x) { 
      super(); //invoking super()
      //rest of construction
  }
}