如何正確同步此模型？

想象一下，有一個按摩師，他有自己的沙龍。他整天都在睡覺，直到一位顧客進入沙龍並喚醒他。如何正確同步此模型？

顧客正在睡覺，而他得到按摩。當按摩師完成時，他會喚醒顧客併爲他的服務獲得報酬。

顧客離開沙龍。

按摩師進入候診室尋找另一個等待（睡覺）的顧客。如果沒有任何按摩師再次上牀睡覺。

使用線程時，這是一個有趣的情況。

public class Aufg1{ 
    public static void main(String args[]){ 
     MassageSalon ms = new MassageSalon(); 
     Customer c = new Customer(ms); 
     Masseur m = new Masseur(ms); 
     m.start(); c.start(); 
    } 
}

Masseur.java

public class Masseur extends Thread{ 

    final MassageSalon salon; 

    public Masseur(MassageSalon pSalon){ 
     salon = pSalon; 
    } 

    public void run(){ 
     while(true){ 
      salon.getNextCustomer(); 
      salon.finishedMassage(); 
     } 
    } 
}

和Customer.java：

public class Customer extends Thread{ 

    final MassageSalon salon; 

    public Customer(MassageSalon pSalon){ 
     salon = pSalon; 
    } 

    public void run(){ 
     while(true){ 
      salon.getMassage(); 
     } 
    } 
}

我有一個類MassageSalon。代碼與我剛剛提到的幾乎一樣。

現在我想用wait(), notify(), notifyAll()確保一切正常，就像我提到的那樣。我已經編輯了MassageSalon類並添加了wait（），notify（）方法。

您認爲wait（）和notify（）的位置是否正確？運行此代碼時，不會調用finishedMassage方法。爲什麼？

public class MassageSalon { 
    private int customerOnCouch = 0; 
    private int customerPaid = 0; 
    private int masseurAvailable = 0; 
    private int masseurBusy = 0; 
    private int masseurDone = 0; 
    private int masseurClose = 0; 


    public synchronized void getNextCustomer() { 

     while(masseurAvailable != masseurClose){ 
      try{ 
       System.out.println("waiting for masseur..."); 
       wait(); 
      }catch(InterruptedException e){ 
       System.out.println(e); 
      } 
     } 

     //masseur is available to handle a new customer 

     System.out.println("masseur is available to handle a new customer"); 

     masseurAvailable++; 

     while(customerOnCouch == customerPaid){ 
      try{ 
       System.out.println("waiting for customer..."); 
       wait(); 
      }catch(InterruptedException e){ 
       System.out.println(e); 
      } 
     } 

     //and is busy as soon as a new customers takes his couch 

     System.out.println("and is busy as soon as a new customers takes his couch"); 

     masseurBusy++; 
    } 

    public synchronized void finishedMassage() { 
     //eventually the masseur finishes the massage 

     System.out.println("eventually the masseur finishes the massage"); 

     masseurDone++; 

     notify(); 

     //and closes the deal as soon as the customer paid 

     System.out.println("and closes the deal as soon as the customer paid"); 

     masseurClose++; 
    } 

    public synchronized void getMassage() { 
     //customer takes a couch 

     System.out.println("customer takes a couch"); 

     customerOnCouch++; 

     notify(); 

     while(masseurBusy != masseurDone){ 
      try{ 
       System.out.println("waiting to finish massage"); 
       wait(); 
      }catch(InterruptedException e){ 
       System.out.println(e); 
      } 
     } 

     //and pays for the massage after it 

     System.out.println("and pays for the massage after it"); 

     customerPaid++; 
    } 
}

來源

2011-05-09 Lost in OWL

看起來像我的作業... – Rom1 2011-05-09 05:51:37

@ Rom1：是的，它是[Dijkstra的睡眠理髮師問題]（http：// en。 wikipedia.org/wiki/Sleeping_barber_problem）。 – 2011-05-09 05:53:27