How can I initialize an ArrayList with all zeroes in Java?

Initialization scoreboard: placing bets on alternatives

While Collections.nCopies() wears the crown for this task, Java courts us with other ways to woo an ArrayList into hosting an exclusive party for zeroes. Here's a cheat sheet:

Option 1: Stream.generate with limit

If you fancy non-primitive objects with an elegant touch of streams:

// To infinity and... nah, just ten zeroes, thanks!
ArrayList<Integer> zeros = Stream.generate(() -> 0)
                                 .limit(10)
                                 .collect(Collectors.toCollection(ArrayList::new));


Option 2: Pre-sizing and loops

When a straightforward loop feels like home:

// Hey, ArrayList! Growth spurt coming...
ArrayList<Integer> zeros = new ArrayList<>(10);
for (int i = 0; i < 10; i++) {
    zeros.add(0); // Zeroes' invasion! Better run for the hills.
}


Option 3: IntStream.range

Whenever IntStream's numeric stream has an appealing swing to it:

// IntStream on stage, ZERO our score!
ArrayList<Integer> zeros = IntStream.range(0, 10)
                                    .mapToObj(i -> 0)
                                    .collect(Collectors.toCollection(ArrayList::new));


Option 4: Arrays.fill with conversion

When you want to rock an array, then boogie to the beat of a list:

// Arrays.fill, meet ArrayList. You will be great friends.
Integer[] zeroArray = new Integer[10];
Arrays.fill(zeroArray, 0);
ArrayList<Integer> zeros = new ArrayList<>(Arrays.asList(zeroArray));


The 'capacity vs. pre-population' showdown

As a Java champ, distinguishing between initial capacity and allocated slots is your homework tonight. Remember, kiddo, the initial capacity is about how many elements an ArrayList can swallow before getting a bellyache. Stuffing its belly with actual values (like succulent zeroes), needs an extra nudge from your code.

Programming faux pas: memory inefficiency

Google might store the world's collective knowledge, but your JVM sure as heck isn't Google! With larger collections, especially within a resource-starved environment, you gotta watch the memory consumption. Showering new Integer(0) all over an intensive loop or with Arrays.fill() only gives you memory-demanding Integer instances. Stick to Collections.nCopies() or Java's Stream API for a more frugal memory profile.

The performance-finale: scalability and RAM

After mastering our zero-flaunting ArrayList, we gotta zoom out and talk BIG: performance and scalability. Think of an ArrayList like a chewing gum — it can stretch (ram expand) beyond its punch (initial capacity), limited only by your JVM's playful mood (system memory or RAM).

Swing to the beat: picking the right approach

The tempo of your code can change based on the rhythm of the requirements. If you stack your ArrayList with immutable objects, avoid Collections.nCopies(), as they'd all bare their teeth at the same object. Choose wisely among the plentiful methods to initialize your ArrayList.