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...


...


...


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