如何获取线程的状态？

发布于 2024-11-06 02:20:54 字数 278 浏览 0 评论 0原文

这就是我定义线程的方式

public class Countdown implements Runnable{

    public Countdown(){
        new Thread(this).start();
    }

    //...
}

如果线程以这种方式启动，是否仍然可以获得线程的状态？喜欢

 Countdown cd = new Countdown();
 cd.getState();

原文

this is how I define my thread

public class Countdown implements Runnable{

    public Countdown(){
        new Thread(this).start();
    }

    //...
}

Is it still possible to get the state of a thread if it is started that way? Like

 Countdown cd = new Countdown();
 cd.getState();

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卸妝后依然美 2024-11-13 02:20:54

如果以这种方式启动线程，是否仍然可以获得线程的状态？

不，事实并非如此。

如果你想能够获取状态，你必须保留对线程的引用；例如

public class Countdown implements Runnable{
    private final Thread t;

    public Countdown(){
        t = new Thread(this);
        t.start();
    }

    public Thread.State getState() {
        return t.getState();
    }
    // ...
}

，顺便说一句，还有其他原因导致这不是一个很好的模式：

如果对 Countdown 对象的引用丢失（例如，由于构造父对象期间出现异常），您将泄漏一个线程。
线程和线程创建会消耗大量资源。如果有很多这样的 Countdown 对象，或者它们的生命周期很短，那么最好使用线程池。

Is it still possible to get the state of a thread if it is started that way?

No. It is not.

If you want to be able to get the state, you have to keep a reference to the Thread; e.g.

public class Countdown implements Runnable{
    private final Thread t;

    public Countdown(){
        t = new Thread(this);
        t.start();
    }

    public Thread.State getState() {
        return t.getState();
    }
    // ...
}

By the way, there are other reasons why this is not a great pattern:

If the reference to the Countdown object is lost (e.g. because of an exception during construction of the parent object), you will leak a Thread.
Threads and thread creation consume a lot of resources. If there are a lot of these Countdown objects, or if they have a short lifetime, then you'd be better of using a thread pool.

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○闲身 2024-11-13 02:20:54

你可以做

public class Countdown implements Runnable{
    private final Thread thread;
    public Countdown(){
        (thread = new Thread(this)).start();
    }

    public Thread.State getState() {
        return thread.getState();
    }
}

You can do

public class Countdown implements Runnable{
    private final Thread thread;
    public Countdown(){
        (thread = new Thread(this)).start();
    }

    public Thread.State getState() {
        return thread.getState();
    }
}

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生来就爱笑 2024-11-13 02:20:54

由于它仅实现 Runnable，因此您必须提供一个包装方法来获取状态：

class Countdown implements Runnable {
    private final Thread thread;

    public Countdown() {
        thread = new Thread(this);
        thread.start();
    }

    public Thread.State getState() {
        return thread.getState();
    }
}

Since it's only implementing Runnable you'll have to provider a wrapper method to get the state:

class Countdown implements Runnable {
    private final Thread thread;

    public Countdown() {
        thread = new Thread(this);
        thread.start();
    }

    public Thread.State getState() {
        return thread.getState();
    }
}

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往事风中埋 2024-11-13 02:20:54

我建议使用 run() 方法并在那里分配正在运行的线程，而不是在 c-tor 中。
一些顺理成章的事情。

public class Countdown implements Runnable{
volatile Object thread = State.NEW;
public void run(){
  this.thread = Thread.currentThread();
  try{
///....
  }finally{
    this.thread = State.TERMINATED;
  }

}

State getState(){
  Object t=this.thread;
  return t instanceof State?((State)t):((Thread)t).getState();
}

}

I'd recommend using the run() method and assign the running thread there, no in the c-tor.
Something along the lines.

public class Countdown implements Runnable{
volatile Object thread = State.NEW;
public void run(){
  this.thread = Thread.currentThread();
  try{
///....
  }finally{
    this.thread = State.TERMINATED;
  }

}

State getState(){
  Object t=this.thread;
  return t instanceof State?((State)t):((Thread)t).getState();
}

}

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