Architects cultivate--6. Single and multithreaded, ThreadLocal

First, ThreadLocal

With thread safety implemented using the WAIT/NOTIFY approach, performance will be greatly impacted. The solution is to use space for time and thread safety without locking.

To take a look at a small example, set in the thread, get is threadlocal

1  Public classconnthreadlocal {2 3      Public Staticthreadlocal<string> th =NewThreadlocal<string>();4     5      Public voidsetth (String value) {6 Th.set (value);7     }8      Public voidGetth () {9System.out.println (Thread.CurrentThread (). GetName () + ":" + This. Th.get ());Ten     } One      A      Public Static voidMain (string[] args)throwsinterruptedexception { -          -         Finalconnthreadlocal ct =Newconnthreadlocal (); theThread T1 =NewThread (NewRunnable () { - @Override -              Public voidrun () { -Ct.setth ("Zhang San"); + ct.getth (); -             } +}, "T1"); A          atThread t2 =NewThread (NewRunnable () { - @Override -              Public voidrun () { -                 Try { -Thread.Sleep (1000); - ct.getth (); in}Catch(interruptedexception e) { - e.printstacktrace (); to                 } +             } -}, "T2"); the          * T1.start (); $ T2.start ();Panax Notoginseng     } -      the}

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Second, single and multi-threaded

The Singleton has a hunger pattern and lazy mode, but these two modes are not available in multithreaded situations. Consideration of new and thread-safe issues in multi-threading generally consider two ways of double check instance and static inner class to implement singleton mode.

Static inner class mode:

1  Public classinnersingleton{2   Private Static classsingleton{3       Private StaticSingleton single =NewSingleton ();4   }      5    PublicSingleton getinstance () {6       returnSingleton.single; 7    }8}

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Double check instance mode:

1  Public classDubblesingleton {2 3     Private StaticDubblesingleton ds;4     5      Public  StaticDubblesingleton Getds () {6         if(ds = =NULL){7             Try {8                 //simulate the preparation time for initializing objects ...9Thread.Sleep (3000);Ten}Catch(interruptedexception e) { One e.printstacktrace (); A             } -             synchronized(Dubblesingleton.class) { -                 if(ds = =NULL){ theDS =NewDubblesingleton (); -                 } -             } -         } +         returnds; -     } +      A      Public Static voidMain (string[] args) { atThread T1 =NewThread (NewRunnable () { - @Override -              Public voidrun () { - System.out.println (Dubblesingleton.getds (). Hashcode ()); -             } -}, "T1"); inThread t2 =NewThread (NewRunnable () { - @Override to              Public voidrun () { + System.out.println (Dubblesingleton.getds (). Hashcode ()); -             } the}, "T2"); *Thread t3 =NewThread (NewRunnable () { $ @OverridePanax Notoginseng              Public voidrun () { - System.out.println (Dubblesingleton.getds (). Hashcode ()); the             } +}, "T3"); A          the T1.start (); + T2.start (); - T3.start (); $     } $      -}

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Architects form--6. Single and multithreaded, ThreadLocal