All methods in runnable class run on a seperate thread or only run() method? Java-CodePudding

Let's say I have a runnable class with two methods:

class ExampleClass implements Runnable { 

public void shutdown()
{
currentThread().interrupt();
}
 
public void run(){
while(!currentThread().isInterrupted()){  
System.out.println("thread is running...");  
}

}

And I go and implement the class somewhere like so and pass it to a thread:

ExampleClass object = new ExampleClass();
Thread sideThread = new Thread( object, "Side Thread");
thread.start();
object.shutdown();

Will all this object and all its methods be running on sideThread or is just the run() method of object on the side thread?

i.e. When I call shutdown() will it actually interrupt the sideThread or will it just interrupt on the main thread where the object is instantiated?

CodePudding user response：

There's no additional magic in Runnable. A Thread takes a Runnable and calls its run method on a new thread. End of story. Any other methods on that object are none of Thread's business. If you want to provide tighter integration between the calling thread and the created thread, that's on you to design.

CodePudding user response：

What Silvio says is correct, any thread can call any method of an object, passing a Runnable to a thread's constructor tells the thread to execute that Runnable's run method. If you want you can pass the same object implementing Runnable to several new threads and let them all run it. No magic here.

When you call Thread.currentThread(), that returns the thread that is executing the code. So as your posted code works now, if 1) a thread A starts a new thread B passing in this Runnable, and next 2) thread A calls shutdown on the Runnable, the result is that the interrupt flag is set on thread A, not on the thread B, the one executing the run method. Probably not what you want. It would be better to keep a reference to the new thread, and call interrupt on that.

Each thread gets a name generated for it. Try adding some lines like:

System.out.println("thread="   Thread.currentThread().getName());

in your code and it will show you which thread is executing. You will see the new thread executing the run method, and the thread that created the new thread running the shutdown method.