为什么一个线程阻止另一个线程运行？

Question

I was going to use threads for each sound in a game engine I'm making. The problem is, whenever I make a new thread that has a while(true) statement, the other thread stops running.

I made a class to test this, and it only prints "goodbye", not "hello". I was wondering how to make the two threads run at the same time.

public class testor {
    public static void main(String args[]){
        testor test=new testor();
        test.runTest();
    }
    class threadTest implements Runnable{

        @Override
        public void run() {
            while(true){
                System.out.println("goodbye");
            }

        }

    }
    public void runTest(){
        threadTest test=new threadTest();
        test.run();
        while(true){
            System.out.println("hello");
        }
    }
}

Answer 1

Since you are doing test.run(); you are only calling the method of that class but not starting the thread.

So in order to answer your question: there is no such a thread stopping the other thread from running? because you have only one Thread that is looping for ever and printing the message System.out.println("goodbye");

If that method is not looping for ever, it would return to the runTest method and then you would see the System.out.println("hello");

Summary:

For starting a Thread use the Thread::start method and not the run .

Answer 2

Using (new ThreadTest()).run() does not start a new Thread , but just invokes the run() method in the current thread.

To run the code in a separate thread do:

(new Thread(new ThreadTest())).start();

Answer 3

That's because you're not creating a new thread. Just naming a class something containing "thread" will not make it a thread, and a Runnable is no thread - it's a class like any other, with no special semantics or behaviour.

It's only special in that you can pass it to a Thread for execution.

public class Testor {
    public static void main(String args[]){
        Testor test=new Testor();
        test.runTest();
    }

    class MyRunnable implements Runnable{
        @Override
        public void run() {
            while(true){
                System.out.println("goodbye");
            }
        }
    }

    public void runTest(){
        Thread testThread = new Thread(new MyRunnable());
        testThread.start();
        while(true){
            System.out.println("hello");
        }
    }
}

You should probably also adhere to the Java coding standards regarding your class and variable names if you do not want your code to look like an alien when combined with most other existing Java code.

Additionally, multithreading is more than just being able to start a new thread. You should also read about synchronisation issues - it's more complicated to do correctly than you might imagine.

Answer 4

Your run method contains an infinite loop. The runTest() method creates the thread which means you'll have 2 execution stacks the main stack, and the runnable threadTest stack. since you're running the thread method first that contains an infinite loop, you'll always get the output "good Bye" .

Remove the infinite loop from run() method.