What's the difference between Thread start() and Runnable run()

Java Threads 101

Getting a grip on Java threads is a necessity for concurrency. The Thread class is the launch pad for new threads, providing a system to run Runnable implementations concurrently. Consider the following:

• Thread cycle: Using start() propels the thread cycle, pushing the thread state to Runnable and laying out the execution environment.
• Execution character: With start(), execution is asynchronous, taking place in a new call stack; whereas run() is predictable, held steadfast in the current call stack.
• Concurrent consequences: start() can gear up your program's efficiency and responsiveness, but it brings with it needs for synchronization and managing complex interactions amid threads.
• Error tackling: When start() is at play, threads can fault independently, whereas run() mishaps are well within the control flow of the invoking thread, making debugging less elaborate.

Strategies for Managing Threads

Let's dive into strategies and tried-and-true practices for handling threads:

Concurrent Execution Best Practices

• Never shout start() twice: Two calls to start() throws an IllegalThreadStateException into the mix and causes a runtime error.
• Safeguard shared resources: While using start(), handle access to shared resources with great care to deter race conditions and outright data corruption.
• Bank on thread pools: For enhanced resource management, capitalize on Executors to deal with several tasks efficiently without the overhead of creating new threads each time.

Optimal Use of run() Method

• Testing trials: Invoke run() directly when you're testing the logic without wanting to stir in concurrency.
• Sequential execution: If the task workload is light or when guaranteed execution order is a need, run tasks in sequence.

Keeping Performance in Check

• CPU-intensive tasks: start() is perfect for tasks that can process in parallel, maximizing CPU utilization.
• I/O-bound tasks: For I/O-bound or blocking operations, performing in multiple threads can lead to better resource usage and spike up system responsiveness.

Visualization

Think it as Rocket Launch vs. Model Rocket in Hand:

Launching a Rocket (🚀): Thread.start()
- Engages a **sequence** to prep, fuel, and light up the engines.
- Woosh! Takes off in a **new thread of execution**.

Holding a Model Rocket (🧑‍🚀🚀): Runnable.run()
- Simply seizing and appreciating the rocket's design.
- Remains in the **current thread of execution**, no blast off.

Key Insight: Thread.start() is akin to a real rocket launch (thrills included!), while Runnable.run() is like pondering over a rocket model (learning, but grounded).

Finer Points of Thread Coding

Keeping Context in Check

• Surprising threads: When you apply start(), the order of execution may not always follow the script, as threads run on their own.
• Predictable behaviour: If the sequence needs to be set in stone, use run() or other higher-level concurrency constructs.

Moving Beyond Runnable: Callable and Future

• Return of the execution: Shift to Callable<V> with Future<V> when you need a result after the thread execution.
• Cancellation and Timeouts: Future allows you to call off execution and apply timeouts, delivering more control over thread activity.

Shutting Down Gracefully

• Stopping threads: Prepare appropriate shutdown hooks or interrupts to make sure that threads using start() don't leave resources in the lurch or keep running indefinitely.

Thread t = new Thread(() -> { /* your code */ });
t.start();
// ... later in program
t.interrupt(); // Polite request: "Hey Thread, can you stop running? Sincerely, your program"
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