Two threads waiting for each other

This code is a phenomenon found when viewing the source code of Android Activitymanagerservice, recording

--Athread run ()--do Some thing---notify main Thread---wait

Mainthread-----notified and do some thing--notify Athread

    public static final Context main (int factorytest) {athread thr = new Athread ();        Thr.start ();                Synchronized (THR) {while (Thr.mservice = = null) {try {thr.wait ();        } catch (Interruptedexception e) {}}}//do some thing ...            Synchronized (THR) {Thr.mready = true;    Thr.notifyall ();//Notify Athread} return context;        }//Activitymanagerservice's internal class static classes Athread extends Thread {activitymanagerservice mservice;        Looper Mlooper;        Boolean mready = false;        Public Athread () {Super ("Activitymanager");            } @Override public void Run () {looper.prepare ();                ... synchronized (this) {mservice = m;                Mlooper = Looper.mylooper (); Watchdog.getinstance (). Addthread (New Handler (MloopER), getName ());                    Notifyall ();//notifies main thread} synchronized (this) {while (!mready) {                    try {wait ();        } catch (Interruptedexception e) {}}} looper.loop (); }    }

Two threads waiting for each other