The iteration order that lies to you

import java.util.*;

/**
 * WARM-UP — 5 minutes. One concept. Hard to fail.
 *
 * A report needs categories printed in the order they were added.
 * This code does not do that reliably.
 *
 * TASKS
 *   1. Predict the output before running.
 *   2. Run it. Was your prediction right? (Most people get this one wrong
 *      for the right reason and right for the wrong reason.)
 *   3. Change ONE word so insertion order is guaranteed.
 *   4. Then change it so the keys come out alphabetically instead.
 */
public class Starter {
    public static void main(String[] args) {
        Map<String, Integer> stock = new HashMap<>();

        stock.put("zebra",    4);
        stock.put("apple",   12);
        stock.put("mango",    7);
        stock.put("banana",   3);
        stock.put("cherry",  19);

        for (Map.Entry<String, Integer> e : stock.entrySet()) {
            System.out.println(e.getKey() + " -> " + e.getValue());
        }

        // Question to answer in a comment before you move on:
        // HashMap makes NO ordering guarantee. So why does the output
        // look stable every single time you run this?
    }
}