Three Stooges Driver

Your Turn — The Five-Stage Adventure

Hit Copy above, paste into JDoodle. Each stage below hands you a problem. Solve it. See what new problem that creates. Repeat. That is exactly how real Java developers work.

💻 Stage 1 — Run It in JDoodle

The code uses args[0], args[1], args[2]. JDoodle has an “Input arguments” field below the code editor — type Moe Larry Curly into it and click Run. The code works exactly as written. First lesson: read the tool’s interface before assuming something won’t work.

🧠 Understand the Signature

Before going further, make sure you can explain every word of this line:

public static void main(String[] args)

• public — any other class (including the JVM) can call this method.
• static — the JVM calls main without creating a ThreeStoogesDriver object first. No new needed.
• void — returns nothing.
• main — the magic name the JVM looks for as the entry point.
• String[] args — an array of Strings passed from the command line (or the “Input arguments” field). args[0] is the first word.

⚠️ Stage 2 — What If There Is No Args Field?

Many classroom environments (certain IDEs, AP Classroom, CodeHS) have no way to pass command-line arguments. Run the code without filling in the args field. You will see an ArrayIndexOutOfBoundsException — a crash, not a style issue. Ask your AI assistant:

You are a patient APCS Java teacher. My Three Stooges Driver crashes
with ArrayIndexOutOfBoundsException when no arguments are provided.
Add a fallback: if args.length < 3, use hardcoded names "Moe", "Larry",
"Curly". If args are provided, use them. Show the complete updated class
with comments explaining the change.

🧹 Stage 3 — Bridge args[] into an ArrayList

Shemp Howard was the fourth Stooge. Try adding him as String stooge4 = args[3]. The print line needs updating. Add a fifth (Joe Besser)? Parallel variables multiply fast. Instead, keep your args[] exactly as it is and bridge it into a dynamic ArrayList using a for-each loop:

import java.util.ArrayList;

ArrayList<String> stooges = new ArrayList<String>();

// Populate the AL from the args array — bridge: fixed array → dynamic list
for (String name : args) {
    stooges.add(name);
}

// Now add stooges beyond what args[] could hold:
stooges.add("Shemp");
System.out.println("The stooges are: " + stooges);

This pattern is the key relationship between primitive arrays and ArrayLists: args[] is fixed in size and given to you by the runtime — you cannot grow it. ArrayList is dynamic — you can keep adding. The for-each loop is the bridge.

📤 Stage 3b — Printing: Arrays vs ArrayLists vs Custom Methods

Before moving on, try printing both structures and compare the output:

System.out.println(args);     // ← try this first — surprising!
System.out.println(stooges);  // ← then this

println(args) prints something like [Ljava.lang.String;@6d06d69c — a memory address, not the contents. Arrays in Java do not override the default toString() method, so Java prints the type ([L = array of objects, java.lang.String) and the object’s memory location. ArrayList, however, does override toString() and prints its contents: [Moe, Larry, Curly, Shemp].

For full control — one name per line, numbered, formatted how you want — write a static helper method:

public static void printArrayList(ArrayList<String> list) {
    for (int i = 0; i < list.size(); i++) {
        System.out.println((i + 1) + ". " + list.get(i));
    }
}

// In main, call it:
printArrayList(stooges);

Output: 1. Moe   2. Larry   3. Curly   4. Shemp — one per line, numbered. Note that list.get(i) retrieves an ArrayList element by index, just as args[i] does for an array. If you want to print the array nicely without a loop, Java’s built-in Arrays.toString(args) works — but you have to import java.util.Arrays first.

⛔ Stage 4 — No Duplicates

Try adding Moe twice. The ArrayList allows it: [Moe, Larry, Curly, Moe]. There is only one Moe. Fix it with a guard:

if (!stooges.contains(candidate)) {
    stooges.add(candidate);
} else {
    System.out.println(candidate + " is already in the list!");
}

🔤 Stage 5 — Case Sensitivity

Now try adding "moe" (lowercase). .contains("moe") returns false — Java’s equals() is case-sensitive. Your duplicate guard fails. Ask your AI to normalize names before checking so that "MOE", "moe", and "Moe" are all treated the same. Hint: toLowerCase() and toUpperCase().

Need Stooge inspiration? Check out the TNT Legacy Thanksgiving movie clips page — it features some classic Three Stooges antics. There’s also Swingin’ the Alphabet, where the Stooges accidentally demonstrate a nested loop.