java - ThreadPoolExecutor backed by PriorityBlockingQueue doesn't seem to work -

i have large number of pictures fetch server, , want fetch pictures higher priority others i've implemented own threadpoolexecutor returns futuretask implements comparable doesn't seem work. tasks more or less processed in order add them queue. i've debugged blockingqueue of threadpoolexecutor , found out when add runnable higher priority, not shifted way @ top of queue. here code

public class prioritythreadpoolexecutor extends threadpoolexecutor {      public prioritythreadpoolexecutor(int corepoolsize, int maximumpoolsize,             long keepalivetime, timeunit unit, blockingqueue<runnable> workqueue) {         super(corepoolsize, maximumpoolsize, keepalivetime, unit, workqueue);     }      protected <t> runnablefuture<t> newtaskforvalue(runnable runnable, t value) {         return new comparablefuturetask<t>(runnable, value);     }      protected class comparablefuturetask<t>      extends futuretask<t> implements comparable<comparablefuturetask<t>> {          private object object;          public comparablefuturetask(runnable runnable, t result) {             super(runnable, result);             object = runnable;         }          @override         @suppresswarnings({ "unchecked", "rawtypes" })         public int compareto(comparablefuturetask<t> o) {             if (this == o) {                 return 0;             }             if (o == null) {                 return -1; // has higher priority null             }             if (object != null && o.object != null) {                 if (object.getclass().equals(o.object.getclass())) {                     if (object instanceof comparable) {                         return ((comparable) object).compareto(o.object);                     }                 }             }             return 0;         }     }  } 

and add tasks pool in way:

public bitmaploader(context context){         mthreadpoolexecutor = new prioritythreadpoolexecutor(10, integer.max_value,//corepool , maxpool                 1l, timeunit.seconds,//keep alive idle threads                 new priorityblockingqueue<runnable>());//priority queue jobs     }  public void queuephoto(string url, imageview imageview, int priority) {          bitmaptoload p = new bitmaptoload(url, imageview, priority);     final runnablefuture<object> futuretask =              mthreadpoolexecutor.newtaskforvalue(new bitmaploaderrunnable(p), null);     log.d("bitmaploader", "scheduling job priority " + priority);     mthreadpoolexecutor.execute(futuretask); } 

my bitmaploaderrunnable implements comparable , when debug compareto method being called. doing wrong? thanks

edit: below code of runnables

private class bitmaploaderrunnable implements runnable, comparable<bitmaploaderrunnable> {         private bitmaptoload bitmaptoload;          public bitmaploaderrunnable(bitmaptoload bitmap) {             this.bitmaptoload = bitmap;         }          @override         public void run() {             try{                 if(imageviewreused(bitmaptoload))                     return;                 thread.sleep(1000);                 bitmap bmp = getbitmap(bitmaptoload.url);                 bitmapcache.put(bitmaptoload.url, bmp);                 if(imageviewreused(bitmaptoload))                     return;                 bitmapdisplayer bd = new bitmapdisplayer(bmp, bitmaptoload);                 mhandler.post(bd);             } catch(throwable th){                 th.printstacktrace();             }         }          @override         public int compareto(bitmaploaderrunnable other) {             return this.bitmaptoload.priority - other.bitmaptoload.priority;         }     } 

the head of priorityqueue least element. if want highest priority first, need reverse comparison.

    @override     public int compareto(bitmaploaderrunnable other) {         return other.bitmaptoload.priority - this.bitmaptoload.priority;     }