Java-java 共享内存的问题

发布于 2017-01-24 11:45:47 字数 2915 浏览 1142 评论 4

在《操作系统概念》一书中看到的例子，用java语言模拟共享内存。
下面是一个BoundedBuffer类，书上说“可以通过让生产者进程和消费者进程共享BoundedBuffer类的实例来实现模拟目的。但是怎么才能让两个进程共享一个实例呢？我试了一下Thread不行啊。

package bit.donkey.OS;

public interface Buffer {
    
    public abstract void insert(int item);
    public abstract int remove();
    
}

///////////////////////////////////////////////////////////////

package bit.donkey.OS;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import static cn.edu.bit.donkey.MyPrint.*;

public class BoundedBuffer implements Buffer{
    //公共内存区
    private static final int BUFFER_SIZE = 5;
    private int count;  // 记录buffer数组中，数据总数
    private int in; //队列首,
    private int out; // 队列尾
    private int[] buffer;
    // 初始化内存
    public BoundedBuffer() {
        count = in = out = 0;
        buffer = new int[BUFFER_SIZE];
    }

    @Override
    //想buffer队列插入一个数据
    public void insert(int item) {
        // TODO Auto-generated method stub
        while(count == BUFFER_SIZE);
        ++ count;
        buffer[in] = item;
        in = (in + 1) % BUFFER_SIZE;
    }

    @Override
    //从buffer队列移除一个数据
    public int remove() {
        // TODO Auto-generated method stub
        int item;
        while(count == 0);
        -- count;
        item = buffer[out];
        out = (out + 1) % BUFFER_SIZE;
        return item;    
    }

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        InputStreamReader stdin = new InputStreamReader(System.in);
        BufferedReader bfr = new BufferedReader(stdin);
        final BoundedBuffer bbf = new BoundedBuffer();
        
        Runnable PRun = new Runnable() {
            
            @Override
            public void run() {
                // TODO Auto-generated method stub
                int n = 0;
                println("in P");
                bbf.insert(n++);
            }
        };
        
        Runnable CRun = new Runnable() {
            
            @Override
            public void run() {
                // TODO Auto-generated method stub
                int n = 0;
                println("in C");
                println(bbf.remove());
            }
        };
        
        // 用两个线程共享实例
        Thread C = new Thread(CRun);
        Thread P = new Thread(PRun);
        while(true) {
            switch(bfr.readLine().charAt(0)){
            case 'C' :
                C.run();
                break;
            case 'P' :
                P.run();
                break;
            }
        }
    }
}