Coding classes for high school students

import java.util.ArrayList;

public class RemoveShort {
    // Bug: removing while counting up skips the next word
    static void removeShortBuggy(ArrayList<String> words) {
        for (int i = 0; i < words.size(); i++) {
            if (words.get(i).length() < 4) {
                words.remove(i);
            }
        }
    }

    // Fix: count down, so no word gets skipped
    static void removeShort(ArrayList<String> words) {
        for (int i = words.size() - 1; i >= 0; i--) {
            if (words.get(i).length() < 4) {
                words.remove(i);
            }
        }
    }

    public static void main(String[] args) {
        String[] start = {"ant", "bee", "tiger", "cat", "zebra"};
        ArrayList<String> a = new ArrayList<String>();
        ArrayList<String> b = new ArrayList<String>();
        for (String w : start) {
            a.add(w);
            b.add(w);
        }
        removeShortBuggy(a);
        removeShort(b);
        System.out.println(a);  // [bee, tiger, zebra]
        System.out.println(b);  // [tiger, zebra]
    }
}

Ours. We compiled and ran it with Java 22 before printing it; the comments show the real output. The buggy version keeps "bee" because removing "ant" shifts "bee" into position 0 just after position 0 was checked.