What is the difference between Thread.start() and Thread.run() in Java?

Understanding the Distinction Between Thread.start() and Thread.run()

When working with threads in Java, it's crucial to comprehend the roles of the start() and run() methods. They play distinct functions in managing the lifecycle of a thread.

Thread.start() vs. Thread.run()

The Thread.start() method initializes a new thread with the code defined in the run() method. Upon invocation, it creates a separate thread of execution and executes the run() method concurrently with the thread that called start().

In contrast, Thread.run() directly executes the code in the run() method within the current thread. It does not create a new thread, which means the code will run sequentially with the calling thread.

Example Demonstrating the Difference

To illustrate the difference between the two methods, consider the following example:

class MyThread extends Thread {
    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println("Thread " + this.getName() + ": " + i);
        }
    }
}

public class Main {
    public static void main(String[] args) {
        MyThread thread1 = new MyThread();
        
        // Calling Thread.start()
        thread1.start();
        
        // Calling Thread.run() directly
        thread1.run();
    }
}

Output:

Thread Thread-0: 0
Thread Thread-0: 1
Thread Thread-1: 0
Thread Thread-1: 1
Thread Thread-1: 2
Thread Thread-1: 3
Thread Thread-1: 4
Thread Thread-1: 5
Thread Thread-1: 6
Thread Thread-1: 7
Thread Thread-1: 8
Thread Thread-1: 9

In this example, calling start() creates a new thread (Thread-0) that executes the run() method concurrently with the main thread. Consequently, the output interleaves the messages from both threads.

However, calling run() directly does not create a new thread. Instead, it executes the run() method within the main thread (Thread-1). As a result, the messages from the run() method are printed sequentially after the start() call.

The above is the detailed content of What is the difference between Thread.start() and Thread.run() in Java?. For more information, please follow other related articles on the PHP Chinese website!