Why is Thread.start() preferred over Thread.run() for thread execution in Java?

Thread Implementation in Java: Comparing Thread.start() and Thread.run()

In Java, a fundamental aspect of concurrency is the creation and execution of threads. Understanding the distinction between Thread.start() and Thread.run() is crucial in this context.

Thread.start() is the method responsible for initiating a new thread of execution. When invoked, it sets up the thread's stack, sets its initial state to runnable, and schedules it to be executed by the Java Virtual Machine (JVM). In contrast, Thread.run() directly executes the code within the run() method on the calling thread, without creating a new one.

Why Use Thread.start()?

Employing Thread.start() over Thread.run() is essential because:

• Multi-threading: Thread.start() creates a new thread, enabling concurrent execution of code.
• Lifecycle Control: Start() initializes the thread's lifecycle, allowing for proper thread management, such as starting, interrupting, and joining.

Direct Invocation of Thread.run()

While it may seem convenient to call Thread.run(), this approach should be avoided for the following reasons:

• Single-Threading: Running run() directly executes the code in the same thread, negating the benefits of multi-threading.
• No Thread Management: Without invoking start(), there is no proper thread management and synchronization.

Example

Consider the following code:

public class ThreadExample {
    public static void main(String[] args) {
        Runnable task = () -> System.out.println("This is a new thread!");
        Thread thread = new Thread(task);

        // Direct invocation of run() - no multi-threading occurs.
        // thread.run();

        // Correct multi-threading using start().
        thread.start();
    }
}

When commenting out the direct invocation of Thread.run(), the output will show that a new thread has been created and ausgeführt, whereas running run() directly will execute the code within the main thread, producing an output without multi-threading.

Conclusion

In Java, calling Thread.start() is the preferred approach for creating and executing threads. Thread.run(), on the other hand, should not be used directly as it hinders multi-threading and thread management capabilities.

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