信號量和用java計算

Question

我已經寫出了我的代碼，指示跨過一個車道橋的北行和南行車，但是我在計數時遇到了一些麻煩。

它應該看起來像：一輛汽車在等待，然後可能是幾個，每次只有一個十字路口，並且每次都在增加。相反，它每次重複相同的三個數字。

我應該用不同的方式聲明我的計數int還是不正確地增加它？我嘗試了很多不同的方式，無法找到真正的問題。

import java.util.concurrent.Semaphore; 
import java.util.concurrent.TimeUnit; 

public class SingleLaneBridge { 

public static void main(String[] args) { 
    final Bridge bridge = new Bridge(); 

    Thread th1 = new Thread(new Runnable() { 

    @Override 
    public void run() { 
     while(true) { 
     Car car = new Car(bridge); 
     Thread th = new Thread(car); 
     th.start(); 
     try { 
      Thread.sleep(5000); 
     } catch (InterruptedException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
     } 
    } 
    }); 

    Thread th2 = new Thread(new Runnable() { 

     @Override 
     public void run() { 
     while(true) { 
      Car car = new Car(bridge); 
      Thread th = new Thread(car); 
      th.start(); 
      try { 
      Thread.sleep(5000); 
      } catch (InterruptedException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
      } 
     } 
     } 
     }); 

     th1.start(); 
     th2.start(); 
    } 
    } 

    class Bridge { 
    private final Semaphore semaphore; 
    public Bridge() { 
    semaphore = new Semaphore(1); 
    } 
    public void crossBridge(Car car) { 
    try { 
     System.out.printf("Car %s is trying to cross the bridge.   \n",car.count++); 
     semaphore.acquire(); 
     System.out.printf("Car %s is crossing the bridge. \n",car.count++); 
     Thread.sleep(5000); 
    } catch(InterruptedException iex) { 
     iex.printStackTrace(); 
    } finally { 
     System.out.printf(" Car %s has crossed the bridge. \n",car.count++); 
     semaphore.release(); 
    } 
    } 
} 

class Car implements Runnable { 
    int count = 0; 
    private String name; 
    private Bridge bridge; 

    public Car(Bridge bridge) { 
    this.bridge = bridge; 
    } 
    public void run() { 
    bridge.crossBridge(this); 
    } 

    public String getName() { 
    return name; 
    } 

    public void setName(String name) { 
    this.name = name; 
    } 
} 

Answer 1

爲什麼它再次重複三個數字又是如此，汽車實例重新每次創建和計數被初始化爲0。

爲了克服這個問題的原因，定義了汽車類的如下得到原子計數爲多線程（汽車）在這裏參與，

class Car implements Runnable { 
    private static AtomicInteger globalCarID = new AtomicInteger(0); 
    int count; 
    ... 

    public Car(Bridge bridge) { 
     this.bridge = bridge; 
     count = globalCarID.incrementAndGet(); 
    } 
} 

並修改System.out.printf在橫橋（）方法，以不增加計數，

下面是完整的代碼，可能成爲你想要的東西，

import java.util.concurrent.Semaphore; 
import java.util.concurrent.TimeUnit; 
import java.util.concurrent.atomic.AtomicInteger; 

public class SingleLaneBridge { 

    public static void main(String[] args) { 
     final Bridge bridge = new Bridge(); 

     Thread th1 = new Thread(new Runnable() { 

     public void run() { 
      while(true) { 
       Car car = new Car(bridge); 
       Thread th = new Thread(car); 
       th.start(); 
       try { 
        Thread.sleep(5000); 
       } catch (InterruptedException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
      } 
     } 
     }); 

     Thread th2 = new Thread(new Runnable() { 

     public void run() { 
      while(true) { 
       Car car = new Car(bridge); 
       Thread th = new Thread(car); 
       th.start(); 
       try { 
        Thread.sleep(5000); 
       } catch (InterruptedException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
      } 
     } 
     }); 

     th1.start(); 
     th2.start(); 
    } 
} 

class Bridge { 
    private final Semaphore semaphore; 
    public Bridge() { 
     semaphore = new Semaphore(1); 
    } 

    public void crossBridge(Car car) { 
     try { 
      System.out.printf("Car %s is trying to cross the bridge. \n",car.count); 
      semaphore.acquire(); 
      System.out.printf("Car %s is crossing the bridge. \n",car.count); 
      Thread.sleep(500); 
     } catch(InterruptedException iex) { 
      iex.printStackTrace(); 
     } finally { 
      System.out.printf(" Car %s has crossed the bridge. \n",car.count); 
      semaphore.release(); 
     } 
    } 
} 

class Car implements Runnable { 
    private static AtomicInteger globalCarID = new AtomicInteger(0); 
    int count; 
    private String name; 
    private Bridge bridge; 

    public Car(Bridge bridge) { 
     this.bridge = bridge; 
     count = globalCarID.incrementAndGet(); 
    } 

    public void run() { 
     bridge.crossBridge(this); 
    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 
}