Challenge 3: A Record Attempting to Extend a Class — Possible Solution
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Broken attempt — NamedThing.java:

public class NamedThing {
    protected String name;
    public NamedThing(String name) { this.name = name; }
}

Broken attempt — LabeledPoint.java:

public record LabeledPoint(int x, int y) extends NamedThing {
    // attempting to extend a regular class from a record
}

Representative compile error:

    LabeledPoint.java:1: error: no interface expected here
    public record LabeledPoint(int x, int y) extends NamedThing {
                                               ^
    1 error

Explanation:
Every record implicitly extends java.lang.Record already -- this
happens automatically the moment the record keyword is used, with no
way to opt out of it. java1-5 established that a class can extend
exactly one other class; java.lang.Record has already permanently
filled that single slot for every record that exists, before the
programmer ever gets a say. There is no syntax that lets a record
additionally extend NamedThing or any other regular class -- the
compiler rejects it immediately, not because of some arbitrary
restriction, but because the single-inheritance slot genuinely has no
room left.

A record CAN still implement any number of interfaces (as shown
earlier in the chapter, e.g. `record Circle(...) implements Shape`),
since implements has no such cap.

WHY THIS WORKS AS AN ANSWER
------------------------------
This reproduces the exact restriction the chapter's warn-box states --
a record cannot extend a class -- and the explanation correctly ties
it back to java1-5's single-inheritance rule combined with the fact
that java.lang.Record already occupies that one slot for every record.