Two lists, one class

import java.util.*;

/**
 * WARM-UP — 5 minutes. One concept. Hard to fail.
 *
 * Two lists that the compiler treats as completely different types.
 * The runtime has a different opinion.
 *
 * TASKS
 *   1. Write down your prediction for every println BEFORE running.
 *   2. Run it.
 *   3. Uncomment the line marked (3). Read the compiler error carefully —
 *      it tells you exactly what the JVM cannot do. Then comment it back.
 *   4. Line (4) compiles. Explain in a comment why `List<?>` is answerable
 *      when `List<String>` is not.
 */
public class Starter {
    public static void main(String[] args) {
        List<String> names = new ArrayList<>();
        List<Integer> scores = new ArrayList<>();

        System.out.println("names class   : " + names.getClass().getName());
        System.out.println("scores class  : " + scores.getClass().getName());
        System.out.println("same class    : " + (names.getClass() == scores.getClass()));
        System.out.println("equal lists   : " + names.equals(scores));

        Object mystery = names;

        // (3) Uncomment this one line. It will not compile.
        // System.out.println("is it strings : " + (mystery instanceof List<String>));

        // (4) This one does compile. Why?
        System.out.println("is it a list  : " + (mystery instanceof List<?>));

        // Question to answer in a comment before you move on:
        // `names` was declared to hold Strings. At runtime, where is that
        // information? Name one place in the class file it still exists.
    }
}