Question

I want to have a constructor with an argument that gets inherited by all child classes automatically, but Java won’t let me do this

class A {
    public A(int x) {
     // Shared code here
    }
}

class B extends A {
    // Implicit (int x) constructor from A
}

class C extends A {
    // Implicit (int x) constructor from A
}

I don’t want to have to write B(int x), C(int x), etc. for each child class. Is there a smarter way of approaching this problem?

Solution #1. Make an init() method that can be called after the constructor. This works, although for my particular design, I want to require the user to specify certain parameters in the constructor that are validated at compile time (e.g. Not through varargs/reflection).

Answer 1

You can’t. If you want to have a parameterized constructor in your base class – and no no-argument constructor – you will have to define a constructor (and call super() constructor) in each of descendant classes.