无法启动线程（实现Runnable）

Question

Could you help me understand why my FreeThread doesn't start a thread. Well, I can see that threads corresponding to HotThreads appear in the debagger. But when I add a FreeThread, no thread appears. If I try to trace it step by step, the cursor doesn't go to the superclass overridden run(), but goes to the start() method of Thread class.

Anyway, any help how to start FreeThreads would be highly appreciated.

public class HotThread implements Runnable{
    @Override
    public void run() {}
}

public class FreeThread extends HotThread {
   public FreeThread(int timeout) {
        super();
        ...  
    }
}

public class ThreadPool {
     public ThreadPool(int numberOfHotThreads) {
         for (int i = 0; i < numberOfHotThreads; i++) {
            HotThread ht;
            Thread t;
                ht = new HotThread(); // Нагруженный поток (есть задача).
                t = new Thread(ht);
                t.start();
         }
     }

    public void addFreeThread() {
        FreeThread ft = new FreeThread();
        Thread t = new Thread(ft);        
        t.start();
    }
} 

Answer 1

 public void run() {} 

So if your run() method really empty, then the thread is starting but immediately finishing and you never see them in the debugger because they've already completed. Try putting a Thread.sleep(10000000); so you can see the thread running. Or as @Radiodef commented, you could put a breakpoint there in the debugger and it should stop there.

No, not empty. There is Thread.currentThread().start(); there.

This is wrong. If you enter the run() method then the thread is already starting. By trying to start() it again, you will cause an IllegalThreadStateException to be thrown because of an incorrect thread state which will kill the running thread immediately. The idea that you can ever start() the current (running) thread is an invalid concept by definition.