Challenge 3: A Forgotten super() Call — Possible Solution
====================================================================

Vehicle.java:

public class Vehicle {
    protected String type;

    public Vehicle(String type) {   // no no-arg constructor exists
        this.type = type;
    }
}

Car.java:

public class Car extends Vehicle {
    public Car() {
        // no explicit super(...) call written here
    }
}

Representative compile error:

    Car.java:2: error: constructor Vehicle in class Vehicle cannot
    be applied to given types;
      public Car() {
             ^
      required: String
      found: no arguments
      reason: actual and formal argument lists differ in length

Explanation:
Because Car's constructor has no explicit super(...) call, Java tries
to insert an implicit no-argument super() call automatically. But
Vehicle only defines a constructor that takes a String -- it has no
no-argument constructor for the implicit call to match. The compiler
can't silently fabricate one, so it fails instead, naming exactly
which constructor it tried and failed to match.

The fix: write super(someTypeString) explicitly as Car's constructor's
first statement, supplying the String Vehicle's constructor requires.

WHY THIS WORKS AS AN ANSWER
------------------------------
This reproduces the chapter's own warn-box exactly: a superclass with
no no-arg constructor and a subclass that omits an explicit super()
call, producing a real compile error precisely because Java's
automatic implicit super() insertion has nothing valid to insert.