java - 如何在java中访问线程的成员？

Question

我有这个线程成员

public int a;

我将线程 id 传递给静态函数，我想做类似的事情

function(long threadId, int a){
    synchronized (threadId){
            threadId.a = a;
            threadId.notify();
    }
}

我知道，线程 id 只是很长，它不会以这种方式工作，那么我如何在函数参数中引用带有 id 的线程？

Answer 1

I know, that threads id is just long and it wont work this way, so how can i reference thread with id i get in functions arguments?

You really can't do what you want to do. You could keep a map of thread-id to associated Thread or Runnable class yourself however and use it to lookup the id.

  Thread thread = new MyThread();
  thread.start();
  idMap.put(thread.getId(), thread);

The right way to do this is to define your own class and deal with the object instead of the thread-id. It is recommended to implement Runnable instead of extending Thread. Something like:

public class MyRunnable impelments Runnable {
    public int a;
    ...
    public void run() {
       // code run in the thread
       synchronized (this) {
          this.wait();
       }
       System.out.println(a);
    }
}

Then you can do:

MyRunnable runnable = new MyRunnable();
Thread thread = new Thread(runnable);
thread.start();
...
public void function(MyRunnable runnable, int a) {
   synchronized (runnable){
       runnable.a = a;
       runnable.notify();
   }
}

Better would be to have a setter on the MyRunnable which encapsulates the process:

public synchronized void setA(int a) {
   this.a = a;
   this.notify();
}

An alternative would be to have the thread can share with the notifying thread a BlockingQueue which saves you from the wait/notify. The main thread (or whomever is calling function) then puts an entity into the queue and the thread pulls it out.