Multithreading--reader Writer's question

Solution One:
Mutual exclusion between reader and writer (semaphore)
The reader is in parallel (if a reader is reading it, the reader can read it without having to apply for permission)

 Public  class readerandwriter {    Private StaticAtomicinteger reader =NewAtomicinteger ();Private StaticAtomicinteger blocked =NewAtomicinteger ();//used to be mutually exclusive to readers    Private StaticSemaphore ws =NewSemaphore (1,true); Public Static void Main(string[] args) {System.out.println ("Hello world!"); Executorservice executors = Executors.newfixedthreadpool (5); Executors.execute (NewWriterr ()); Executors.execute (NewReaderr (1)); Executors.execute (NewReaderr (2)); Executors.execute (NewReaderr (3)); Executors.execute (NewReaderr (4));    Executors.shutdown (); }StaticClass Writerr implements Runnable { Public void Run(){Try{ while(true) {Ws.acquire (); Write ();//system.out.println ("Waiting:" + ws.getqueuelength () + "-------" +blocked.get ());Ws.release (blocked.get () = =0?1: Blocked.get ()); Blocked.set (0); }            }Catch(Interruptedexception ex) {            }        }Private Static void Write(){Try{System.out.println ("Writing ..."); Thread.Sleep ((NewRandom (). Nextint (2))* +); System.out.println ("writed!"); }Catch(Interruptedexception ex) {            }        }    }StaticClass Readerr implements Runnable {Private intId Public Readerr(intID) { This. id = ID; } Public void Run(){Try{ while(true){if(Reader.get () = =0) {blocked.getandincrement ();                    Ws.acquire (); }//atomically adds 1 to the current valueReader.getandincrement (); Read ();//atomically subtract the current value by 1Reader.getanddecrement ();if(Reader.get () = =0) {ws.release (); }//Sell time, not excessive competition with writer                    //system.out.println ("[" +id+ "] time to sell");Thread.Sleep (6000); }            }Catch(Interruptedexception ex) {            }        }Private void Read(){Try{System.out.println ("["+id +"]reading ..."); Thread.Sleep ((NewRandom (). Nextint (Ten))* +); System.out.println ("["+id+"]read!"); }Catch(Interruptedexception ex) {            }        }    }}

Solution Two:
Lock with synchronized

 Public  class ReaderAndWriter1 {     Public StaticFile File =NewFILE (); Public Static void Main(string[] args) {System.out.println ("Hello world!"); Executorservice executors = Executors.newfixedthreadpool (5); Executors.execute (NewWriterr ()); Executors.execute (NewReaderr (1)); Executors.execute (NewReaderr (2)); Executors.execute (NewReaderr (3)); Executors.execute (NewReaderr (4));    Executors.shutdown (); }StaticClass Writerr implements Runnable { Public void Run(){ while(true) {file.write (); }        }    }StaticClass Readerr implements Runnable {Private intId Public Readerr(intID) { This. id = ID; } Public void Run(){Try{ while(true) {File.read (ID);//Sell time, not excessive competition with writer                    //system.out.println ("[" +id+ "] time to sell");Thread.Sleep (6000); }            }Catch(Interruptedexception ex) {}}}}class FILE {//number of readers    Private StaticAtomicinteger reader =NewAtomicinteger (0);//number of written by    Private StaticAtomicinteger writer =NewAtomicinteger (0);//write file     Public void Write(){Try{synchronized(reader) {if(Reader.get () >0) {reader.wait (); }            }synchronized(writer)                {writer.getandincrement (); System.out.println ("Writing ..."); Thread.Sleep ((NewRandom (). Nextint (2))* +); System.out.println ("writed!");                Writer.getanddecrement ();            Writer.notifyall (); }        }Catch(Interruptedexception ex) {        }    }//Read file     Public void Read(intID) {Try{synchronized(writer) {if(Writer.get () >0) {writer.wait ();            }} reader.getandincrement (); System.out.println ("["+id +"]reading ..."); Thread.Sleep ((NewRandom (). Nextint (Ten))* +); System.out.println ("["+id+"]read!"); Reader.getanddecrement ();synchronized(reader) {if(Reader.get () = =0) {reader.notify (); }            }        }Catch(Interruptedexception ex) {        }    }}

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Multithreading--reader Writer's question