java - 读者/作者问题的优先级

Question

我为 Java 中的读写器问题开发了一个解决方案(有关此的一些信息 http://lass.cs.umass.edu/~shenoy/courses/fall08/lectures/Lec11.pdf )。

但是我不确定如何修改代码以有利于作者或给予读者和作者相同的优先级。我的代码属于什么类型的问题？我该如何看待它？

public class ReaderWriter{


    int numberOfReaders;
    int numberOfWriters;

    public ReaderWriter(){
        this.numberOfReaders = 0;
        this.numberOfWriters = 0;
    }

    public synchronized void requestRead(){
        while(this.numberOfWriters > 0)
            wait();

        this.numberOfReaders++;
    }

    public synchronized void releaseRead(){
        this.numberOfReaders--;
        notifyAll();
    }

    public synchronized void requestWrite(){
        while(this.numberOfReaders > 0 || this.numberOfWriters > 0)
            wait();

        this.numberOfWriters++; 
    }

    public synchronized void releaseWrite(){
        this.numberOfWriters--;
        notifyAll();
    }
}

Answer 1

你的版本有利于读者(并且可能会让作家挨饿)。这是一个有利于作家的修改版本(并且可能会让读者挨饿):

    int numberOfReaders;
    int numberOfWriters;
    int numberOfRequestedWriters;  // ++

    public ReaderWriter(){
        this.numberOfReaders = 0;
        this.numberOfWriters = 0;
        this.numberOfRequestedWriters = 0; // ++
    }

    public synchronized void requestRead(){
        while(this.numberOfWriters > 0  // --
              || this.numberOfRequestedWriters > 0) // ++
            wait();

        this.numberOfReaders++;
    }

    public synchronized void releaseRead(){
        this.numberOfReaders--;
        notifyAll();
    }

    public synchronized void requestWrite(){
        this.numberOfRequestedWriters++; // ++
        while(this.numberOfReaders > 0 || this.numberOfWriters > 0)
            wait();
        this.numberOfRequestedWriters--; // ++

        this.numberOfWriters++; 
    }

    public synchronized void releaseWrite(){
        this.numberOfWriters--;
        notifyAll();
    }
}