课程设计——利用信号量实现读-写者问题（JAVA）

package cn.Douzi.ReadWriter;

import java.util.Scanner;

public class ReadWrite {

    static public int count = 0;                //读者数量
    static public int wcnt = 0;                 //写者数量
    static public int REATIME = 1500;           //读者休眠时间
    static public int WRITIME = 1000;           //写者休眠时间
    static public boolean wFlag = false;        //写信号 - 用于实现写优先
    static public boolean rFlag = false;        //读信号
    static public Mutex mutex = new Mutex(1);   //用于保护更新count变量时的互斥
    static public Mutex rw = new Mutex(1);      //用于保证读者和写者互斥的访问文件
    static public StringBuilder file = new StringBuilder("空");

    public static void main(String[] args) {

        System.out.println("|-----------------------------------------------------------|");
        System.out.println("|                                                           |");
        System.out.println("|                   Welcome to My System !                  |");
        System.out.println("|                    ↖   By Douzi   2017 ↗                                                                        |");
        System.out.println("|                      读写程序开始进行                                                                               |");
        System.out.println("|                                                           |");
        System.out.println("|-----------------------------------------------------------|");

        Scanner scaner = new Scanner(System.in);

        System.out.println("设置读进程休眠时间: ");
        REATIME = scaner.nextInt();
        System.out.println("设置写进程休眠时间: ");
        WRITIME = scaner.nextInt();

        Writer w = new Writer();
        Reader r = new Reader();

        Thread t1 = new Thread(w);
        Thread t2 = new Thread(r);
        t1.start(); t2.start();
    }

}

class Writer implements Runnable {

    @Override
    public void run() {
        // TODO Auto-generated method stub
        while (true) {
            try {
                Thread.sleep(ReadWrite.WRITIME);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            if (!ReadWrite.wFlag && !ReadWrite.rFlag) {      //在无写进程请求时进入
                synchronized (ReadWrite.rw)  {               //互斥访问共享文件
                    System.out.println("写文件...........");   //写入
                    System.out.println("文件:" + ReadWrite.wcnt + "\n");
                    ReadWrite.file.append("文件:" + ReadWrite.wcnt++ + " - ");
                    if (ReadWrite.wcnt % 5 == 0) {
                        ReadWrite.file.append("\n");
                    }
                }
            } else {
                break;
            }
        }
    }

}

class Reader implements Runnable {

    @Override
    public void run() {
        // TODO Auto-generated method stub
        while (true) {
            try {
                Thread.sleep(ReadWrite.REATIME);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            if (!ReadWrite.wFlag) {                  //在无写进程请求时进入
                synchronized (ReadWrite.mutex) {     //互斥访问count变量
                    if (ReadWrite.count == 0) {      //当第一个读进程读共享文件时
                        ReadWrite.rFlag = true;
                    }
                    ReadWrite.count++;               //读者计数器
                    System.out.println("读者数:" + ReadWrite.count );
                }
            } else {
                System.out.println("已有写进程,暂不读文件............\n");
                break;
            }
            System.out.println("读文件: " + ReadWrite.file + "\n");
            synchronized (ReadWrite.mutex) {        //互斥访问count变量
                ReadWrite.count--;                  //读者计数器减1, 只有读者=0时候，才能继续写
                if (ReadWrite.count == 0) {         //当最后一个读进程读完共享文件
                    ReadWrite.rFlag = false;
                }
            }
        }
    }
}

class Data {
    private int data;

    public Data(int data) {
        super();
        this.data = data;
    }

    public int getData() {
        return data;
    }
}

class Mutex {
    private int mutex;

    public Mutex(int mutex) {
        super();
        this.mutex = mutex;
    }

}

class Buffer {
    private int full;
    private int empty;
    public Buffer(int full, int empty) {
        super();
        this.full = full;
        this.empty = empty;
    }
}