使用信號量來實現監視器

Question

我想使用信號量來實現監視器。我創建了2個課程。緩衝區和ThreadDemo。在Buffer類，我創建方法的put（）和get（）（我得到的代碼從此頁）

public void put(int input) throws InterruptedException { 
    monitorSemaphore.acquire(); 
    boolean acquired = false; 
    while (numberInBuffer == size) { 
     // Equivalent of wait() 
     if (acquired) { 
      dec(); 
      notifyCalled.release(); 
     } 
     inc(); 
     monitorSemaphore.release(); 
     notifyCalled.acquire(); 
     monitorSemaphore.acquire(); 
     acquired = true; 
    } 

    // Critical section 
    buffer[last] = input; 
    last = (last + 1) % size; 
    numberInBuffer++; 

    // Equivalent of notifyAll() 
    for (int i = val(); i > 0; i--) { 
     dec(); 
     notifyCalled.release(); 
    } 

    monitorSemaphore.release(); 
} 

public int get() throws InterruptedException { 
    monitorSemaphore.acquire(); 

    boolean acquired = false; 
    while (numberInBuffer == 0) { 
     // Equivalent of wait() 
     if (acquired) { 
      dec(); 
      notifyCalled.release(); 
     } 
     inc(); 
     monitorSemaphore.release(); 
     notifyCalled.acquire(); 
     monitorSemaphore.acquire(); 
     acquired = true; 
    } 

    // Critical section 
    int temp = buffer[start]; 
    start = (start + 1) % size; 
    numberInBuffer--; 

    // Equivalent of notifyA(ll) 
    for (int i = val(); i > 0; i--) { 
     dec(); 
     notifyCalled.release(); 
    } 

    monitorSemaphore.release(); 

    return temp; 
} 

在課堂上TestThread，我創建Thread-T1，線程T2。但我不能在類Buffer中調用put和Get。

public class TestThread extends Thread { 
private Thread t; 
    private String threadName; 

    public TestThread(String name) { 
     threadName = name; 
     System.out.println("Creating " + threadName); 
    } 

    public void run() { 
     System.out.println("Running " + threadName); 
     try { 
      put(2);//I can't call this method 
      Thread.sleep(5000); 
      get(); // 
      Thread.sleep(5000); 
     } catch (InterruptedException e) { 
     System.out.println("Thread " + threadName + " interrupted."); 
    } 
    System.out.println("Thread " + threadName + " exiting."); 
    } 


    public void start() 
    { 
     System.out.println("Starting " + threadName); 
     if (t == null) 
     { 
     t = new Thread (this, threadName); 
     t.start(); 
     } 
    } 


public static void main(String[] args) { 

     TestThread T1 = new TestThread("Thread-1"); 
     T1.start(); 

     TestThread T2 = new TestThread("Thread-2"); 
     T2.start(); 

}} 

如果我的TestThread類中的代碼不正確，請告訴我。謝謝！

Answer 1

我想......假設您在Buffer類中定義了get（）和put（）方法。然後，在調用in-class方法之前，應該先初始化類實例。像下面的代碼：

public class TestThread extends Thread { 
    private Thread t; 
    private String threadName; 
    private Buffer buffer; 

    public TestThread(String name, Buffer buffer) { 
     threadName = name; 
     this.buffer = buffer; 
     System.out.println("Creating " + threadName); 
    } 

    public void run() { 
     System.out.println("Running " + threadName); 
     try { 
      buffer.put(2);//I can't call this method 
      Thread.sleep(5000); 
      buffer.get(); // 
      Thread.sleep(5000); 
     } catch (InterruptedException e) { 
     System.out.println("Thread " + threadName + " interrupted."); 
    } 
    System.out.println("Thread " + threadName + " exiting."); 
    } 
}