Question

我已经使用同步类编写了一些代码，它可以工作，但不是我想要的。我需要它只在缓冲区为空时才将糖果放入有界缓冲区数组中，然后put线程不会重新填充，直到缓冲区再次为空。我尝试了几件不同的东西，但似乎没有任何工作。

import java.util.Scanner;

class CandyBowl
{
    private int[] buf;
    private int in = 0;
    private int out= 0;
    private int count = 0;
    private int size;

CandyBowl(int size)
{
    this.size = size;
    buf = new int[size];
}

synchronized public void put(int o)
{
    while (count==size)
    {
        System.out.println("Candy bowl is full!");
        try
        {
            wait();
        }
        catch(InterruptedException e){}
    }
        //System.out.println("put");
        buf[in] = o;
        ++count;
        in=(in+1) % size;
        notifyAll();
}

synchronized public int get()
{
    while (count==0)
    {
        System.out.println("Candy bowl is empty! Get the TA!");
        try
        {
            wait();
        }
        catch(InterruptedException e){}
    }
    //System.out.println("get");
    int ret_val = buf[out];
    --count;
    out=(out+1) % size;
    notifyAll();
    return (ret_val);
}
}

class PieceOfCandy
{
   private int candy = 0;

   public synchronized int getNextPiece()
   {


 return ++candy;
   }
}

class Producer extends Thread
{

    CandyBowl buf_;
    PieceOfCandy piece;

    Producer(CandyBowl b, PieceOfCandy kitkat)
    {
        buf_ = b;
        piece = kitkat;
    }

    public void run()
    {
        try
        {
            while(true)
            {
                buf_.put(piece.getNextPiece());
                Thread.sleep(250);
            }
        }
        catch (InterruptedException e)
        {
            System.out.println("TA: I need to buy more candy!");
        }
    }
}

class Consumer extends Thread
{
    CandyBowl buf_;
    char ident;

    Consumer(CandyBowl b, char id)
    {
        buf_ = b;
        ident = id;
    }

    public void run()
    {
        try
        {
            int value;
            while(true)
            {
                value = buf_.get();
                System.out.println("Professor " + ident + " took candy " + value);
                Thread.sleep(1000);
            }
        }
        catch (InterruptedException e)
        {
          System.out.println("Professors " + ident + ": I guess I'll teach now.");
        }
    }
}

public class OS_BoundedBuffer
{
    public static void main (String args[])
    {
        char id = 'A';
        PieceOfCandy candy = new PieceOfCandy();

        Scanner sc = new Scanner(System.in);
        System.out.print("How many Professors want to think? ");
        final int numProfs = sc.nextInt();

        CandyBowl bowl = new CandyBowl(10);
        System.out.println();

        Producer teachAssist = new Producer(bowl, candy);
        Consumer profs[] = new Consumer[numProfs];

        for (int i = 0; i < numProfs; i++)
        {
            profs[i] = new Consumer(bowl, id);
            id = (char)(id + '\001');
        }

        teachAssist.start();

        for (int i = 0; i < numProfs; i++)
             profs[i].start();

        try
        {
             Thread.sleep(30000);

             System.out.println("Main: I'm tired of waiting!");
             for(int i = 0; i < numProfs; i++)
                profs[i].interrupt();
             teachAssist.interrupt();
             for(int i = 0; i < numProfs; i++)
                profs[i].join();
             teachAssist.join();
        }
        catch (InterruptedException e) {}
    }
}

任何帮助将不胜感激！

Answer 1

可能导致错误的一件事是您正在同步访问一个资源的两种方法。不要在方法上进行同步，而是尝试在Object或buf上进行同步。这是一个问题，因为多个线程正在修改count和buf的元素如果需要一个例子来说明竞争条件是如何运作的，请告诉我。

Java线程程序

1 个答案: