Since your super class Person doesn’t have a default constructor, in your sub classes (Student and Staff), you must call the super class constructor as the first statement. You should define your sub class constructors like this:
You get this error because a class which has no constructor has a default constructor, which is argument-less and is equivalent to the following code: However since your BaseClass declares a constructor (and therefore doesn’t have the default, no-arg constructor that the compiler would otherwise provide) this is illegal – a class that extends BaseClass can’t call super(); because … Read more