Java线程是否会被垃圾回收

 import java.lang.ref.WeakReference;
public class TestThread {
  public static void testUnreferencedThread() {
        // anonymous class extends Thread
        Thread t = new Thread() {
            public void run() {
                // infinite loop
                while (true) {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                    }
                    // as long as this line printed out, you know it is alive.
                    System.out.println("thread is running...");
                }
            }
        };
        t.start();
        WeakReference<Thread> wr = new WeakReference<Thread>(t);
        t = null;
        // no more references for Thread t
        // another infinite loop
        while (true) {
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
            }
            System.gc();
            StringBuilder sb = new StringBuilder();
            sb.append("Executed System.gc(),");
            if(wr.get()==null) {
              sb.append(" thread variable has been GCed");
            } else {
              sb.append("WeakReference still keep ").append(wr.get());
            }              
            System.out.println(sb.toString());
        } // The program will run forever until you use ^C to stop it
  }
  
    public static void main(String[] s) {
      testUnreferencedThread();
    }
}

 thread is running...
thread is running...
thread is running...
Executed System.gc(),WeakReference still keep Thread[Thread-0,5,main]
thread is running...
thread is running...
thread is running...
Executed System.gc(),WeakReference still keep Thread[Thread-0,5,main]
thread is running...
thread is running...
...
...
...