Java示例-线程的ID

public class Main extends Object implements Runnable {
   private ThreadID var;
   public Main(ThreadID v) {
      this.var = v;
   }

   public void run() {
      try {
         print("var getThreadID =" + var.getThreadID());
         Thread.sleep(2000);
         print("var getThreadID =" + var.getThreadID());
      } catch (InterruptedException x) {}
   }

   private static void print(String msg) {
      String name = Thread.currentThread().getName();
      System.out.println(name + ": " + msg);
   }

   public static void main(String[] args) {
      ThreadID tid = new ThreadID();
      Main shared = new Main(tid);
      try {
         Thread threadA = new Thread(shared, "threadA");
         threadA.start();
         Thread.sleep(500);

         Thread threadB = new Thread(shared, "threadB");
         threadB.start();
         Thread.sleep(500);

         Thread threadC = new Thread(shared, "threadC");
         threadC.start();
      } catch (InterruptedException x) {}
   }
}

class ThreadID extends ThreadLocal {
   private int nextID;
   public ThreadID() {
      nextID = 10001;
   }

   private synchronized Integer getNewID() {
      Integer id = new Integer(nextID);
      nextID++;
      return id;
   }

   protected Object initialValue() {
      print("in initialValue()");
      return getNewID();
   }

   public int getThreadID() {
      Integer id = (Integer) get();
      return id.intValue();
   }

   private static void print(String msg) {
      String name = Thread.currentThread().getName();
      System.out.println(name + ": " + msg);
   }
}