Problem of the Day

Friday, January 23, 2026

Problem:

Consider the following code segment, which successfully declares, initializes, and manipulates the ArrayList monsters.

ArrayList<String> monsters = new ArrayList<String>();
monsters.add("Godzilla");
monsters.add("Frankenstein");
monsters.add("The Thing");
monsters.add(2, "Dracula");
monsters.add("Mothra");
monsters.remove(1);
monsters.set(2, "Wolf Man");

What is the final state of the ArrayList, in order from lowest-index to highest-index?

1. {"Godzilla", "Dracula", "Wolf Man", "Mothra"}
2. {"Godzilla", "Frankenstein", "The Thing", "Mothra"}
3. {"Godzilla", "Wolfman", "The Thing", "Mothra"}
4. {"Frankenstein", "Dracula", "Wolfman"}

Show solution:

ArrayList<String> monsters = new ArrayList<String>(); →
    {}
monsters.add("Godzilla"); →
    {"Godzilla"}
monsters.add("Frankenstein"); →
    {"Godzilla", "Frankenstein"}
monsters.add("The Thing"); →
    {"Godzilla", "Frankenstein", "The Thing"}
monsters.add(2, "Dracula"); →
    {"Godzilla", "Frankenstein", "Dracula", "The Thing"}
monsters.add("Mothra"); →
    {"Godzilla", "Frankenstein", "Dracula", "The Thing", "Mothra"}
monsters.remove(1); → 
    {"Godzilla", "Dracula", "The Thing", "Mothra"}
monsters.set(2, "Wolf Man"); →
    {"Godzilla", "Dracula", "Wolf Man", "Mothra"}