To run a thread in Java, call start() and let the JVM manage the thread's run.

What happens when a Java program decides it’s got more to do than one thread can handle? In today’s apps—think real-time data processing, responsive UIs, or background maintenance tasks—threads are the tiny workers that keep everything moving without freezing the front end. If you’ve ever watched a kitchen run with one chef trying to juggle a dozen orders, you’ll get the gist: multiple threads let tasks proceed in parallel, so nothing sits idle for long.

Let me explain the simplest, most crucial move you’ll ever make when you’re dealing with threads in Java: starting a thread correctly. If you’re looking at a question like the Revature topic that often crops up in assessments, you’ll see it boiled down to this basic choice. The correct answer is to invoke thread.start(). Here’s the thing: calling start() isn’t just a formality. It’s what hands the baton to the Java Virtual Machine (JVM) so a brand-new call stack can take over and run the code you’ve put in the thread’s run() method.

Why start()? A quick mental model helps. You create a thread object, which is like reserving a lane on a racetrack. The thread is prepared to run, but it waits for the signal to actually begin. When you call start(), you’re signaling that signal. The JVM then creates a separate path, a new call stack, for that thread and calls its run() method. That run() method is where your actual task—whatever you want that thread to do—takes shape. Everything after that is about timing, synchronization, and making sure the thread cooperates with the rest of your program.

Now, you might wonder: what if I just call run() directly? Won’t that run the code in the thread’s run() method? Here’s the easier-to-muck-up detail: calling run() directly does not start a new thread. It merely executes the code in the current thread’s context. So you won’t get true parallelism; you’ll just be running the code inline, as part of the same thread that invoked run(). It’s like inviting a second worker to help, but making them work in the same workspace as you without giving them a separate desk. The net effect? Your program behaves as if it’s single-threaded, which defeats the purpose of introducing multi-threading in the first place.

If you’re reviewing typical options in a quiz or interview prompt—A. Call thread.init(), B. Invoke thread.start(), C. Call thread.begin(), D. Use thread.execute()—the correct pick is B. Invoke thread.start(). The other choices simply aren’t part of Java’s threading model. They sound plausible in other contexts or languages, but in Java they don’t wire up to the lifecycle of a thread. It’s easy to see why folks trip up here: there’s a lot of “thread-y” language floating around, and it’s tempting to treat start() like a generic initiator. But it isn’t. It’s the precise signal that the JVM has a new thread in motion.

Let’s pause for a moment and connect this to some practical, everyday coding life. Imagine you’re building a small app that downloads data in the background while you keep the UI responsive. You’d create a thread whose run() method handles the download. Then you’d call start() to kick it off, so the download happens concurrently with the rest of your program. If you mistakenly run the download code directly inside the UI thread by calling run(), the download would block the interface. It’s not just about performance; it’s about user experience. The UI would feel sluggish, perhaps even frozen, while the download grinds away. The start() method is what prevents that stalling and keeps your program feeling snappy.

A quick note on lifecycle little quirks that catch folks off guard. The start() method can be called only once per thread instance. If you try to start the same thread again, you’ll encounter an IllegalThreadStateException. That’s a tidy reminder that a thread’s lifecycle is pretty strict: create once, start once, then run, and eventually finish. If you need to repeat work, you’d typically create a new Thread object and start it anew. It’s a small detail, but one that saves you a lot of debugging headaches when you’re building responsive apps.

Now, a natural digression that still ties back to the core concept: the difference between multithreading and asynchronous-looking code. In Java, you can achieve similar effects with frameworks and APIs that schedule tasks, like ExecutorService, Futures, or CompletableFuture. These abstractions don’t replace the need to start a thread per se, but they give you cleaner control over how tasks are executed and how results come back. They’re the modern way to structure work without ad-hoc thread creation. Still, at the raw level, the moment you want a new thread to take on work, start() is your friend.

A few practical tips you’ll appreciate when you’re sorting through Revature topics or similar technical questions:

• Start with the basics: remember that start() kicks off a new thread and leads the JVM to call run() in that new thread. Keep that mental map in place.

• Don’t confuse start() with run(): run() is the “do the thing” method, but start() is the door that opens a new path for it.

• Respect the one-start rule: a given Thread instance should be started once. If you need repeated work, instantiate a new Thread object.

• If you’re coordinating multiple threads, plan for join() and synchronization: start() is just the first step. Real-world apps need a way to bring threads back together safely.

• Consider higher-level APIs when complexity grows: ExecutorService, ThreadPoolExecutor, and related patterns help manage resources as your app scales. The core idea remains the same, but the plumbing becomes cleaner.

Let me circle back with a relatable analogy. Think of a thread as a coworker who can take a task off your plate. You hand them the task by starting the thread (via start()), and then you trust the coworker to handle it—while you go on with other work. If you try to tell that coworker to do the task by speaking through you (calling run()), you’re effectively asking them to work in the same workspace as you and centralize everything. That’s not multitasking; that’s delegation without separation. The start() call is what ensures there’s actual parallel effort.

If you’re studying Revature-focused topics for a broader understanding, you’ll notice a core theme: clarity about how Java handles concurrency. The idea isn’t to fear threads, but to harness them with intention. A firm grasp of start() versus run() opens the door to more advanced patterns, like avoiding race conditions or minimizing contention with proper synchronization. And yes, you’ll encounter more nuanced constructs—volatiles, synchronized blocks, locks—but the first step remains the same: start the thread, let it run, then coordinate as needed.

A quick, friendly recap before we wrap. The initial action to execute a thread in Java is to invoke thread.start(). This method tells the JVM to set up a separate call stack for the new thread and to call its run() method, letting the thread execute in parallel with the rest of your program. Calling run() directly won’t create a new thread; it just runs the code in the current thread. The other options—init(), begin(), execute()—aren’t part of the threading model for starting a thread in Java, so they won’t achieve that parallel action you’re aiming for.

As you continue exploring topics like this, keep the mental image of the two paths—the main thread and the new worker—narrating your code’s flow. You’ll find that understanding the small, decisive moves like start() makes the bigger picture click. Java’s concurrency model can feel a bit technical at first glance, but with the right mental models, it starts to feel natural—almost intuitive.

If you’re ever unsure, a simple litmus test helps: “Does this action create a new path of execution, separate from the current one?” If the answer is yes, you’re probably at start() territory. If the code is meant to run in the current thread, you’re likely looking at something like run()—not a new thread, but a direct, straightforward execution.

So next time you’re parsing a question about threading, or reviewing a code snippet in a Revature-related topic, keep that contrast in mind. Start the thread to begin parallel work, and let run() do the actual task in that new lane. It’s a small rule with big impact, and it’s one of those fundamentals that quietly powers scalable, responsive Java applications.