如果我在java中调用我的主类的函数，从具有自己的线程的其他对象，这个函数将在单独的线程中运行？

Question

Let's say I create Producer from my main. Then, this producer creates it's own thread, and when it produces something calls a function main.addProduct() . Will this function execute in the same thread as the producer that called it? Or will it work in the same thread as main, meaning it will wait till all the other tasks are finished before solving it?

To illustrate

public class MainP{
  public static void main(String[] args) {
        Producer p1 = new producer;
        Producer p2 = new producer;
        Producer p3 = new producer;
        p1.start();
        p2.start();
        p3.start();
        System.out.println("I'm ugly");
  }

  public static void prettyFunction(){
        System.out.println("I'm pretty!");
  }

}

public class Producer  extends Thread{
  public void run(){
        while(true)
              MainP.prettyFunction();
}

And the question is whether the result will be

  I'm ugly
  I'm pretty!
  I'm pretty!
  I'm pretty!
  ...

or

  I'm pretty!
  I'm pretty!
  I'm pretty!
  I'm ugly
  I'm pretty!
  I'm pretty!
  I'm pretty!
  ...

Answer 1

Threads don't care in which objects they are running. Unless they are joined with another thread (ie they are stopped) or if they run into code that generates a new thread, everything stays in the thread.

Obviously if you call a method from multiple threads, especially methods that has side effects such as main.addProduct() , you need to think about synchronization.

Answer 2

If main.addProduct() is being called from your producer thread, then it's that thread where the method is being executed, not your main thread. It will not wait until other tasks in your main thread are complete, so there is a potential for synchronization bugs here.