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Thread: Reader Writer Project

  1. #1
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    Default Reader Writer Project

    Hi guys, this is my code but I got some error. I think I made a mistake in main part. Buto I dont know how can I fix it. Anyone can help me?
    I have an error in executer part. These are my errors:
    The constructor Writer(ReadWriteLock) is undefined
    The constructor Reader(ReadWriteLock) is undefined
    Also this is my code:

    public class ReaderWriter{

    public static void main(String args[]){

    ReadWriteLock RW = new ReadWriteLock();
    ExecutorService executorService = Executors.newCachedThreadPool();

    executorService.execute(new Writer(RW));
    executorService.execute(new Writer(RW));
    executorService.execute(new Writer(RW));
    executorService.execute(new Writer(RW));

    executorService.execute(new Reader(RW));
    executorService.execute(new Reader(RW));
    executorService.execute(new Reader(RW));
    executorService.execute(new Reader(RW));

    }
    }
    //Writer class
    class Writer implements Runnable
    {
    private ReadWriteLock rwlock;
    private int writerNum;

    public Writer(int w, ReadWriteLock rw) {
    writerNum = w;
    rwlock = rw;
    }

    public void run() {
    while (true){
    SleepUtilities.nap();

    System.out.println("writer " + writerNum + " wants to write.");
    rwlock.WriteLock(writerNum);

    SleepUtilities.nap();

    rwlock.WriteUnLock(writerNum);
    }
    }
    }

    //Reader class
    class Reader implements Runnable
    {

    private ReadWriteLock rwlock;
    private int readerNum;

    public Reader(int readerNum, ReadWriteLock database) {
    this.readerNum = readerNum;
    this.rwlock = database;
    }

    public void run() {
    while (true) {
    SleepUtilities.nap();
    System.out.println("reader " + readerNum + " wants to read.");
    rwlock.ReadLock(readerNum);

    // you have access to read from the database
    // let's read for awhile .....
    SleepUtilities.nap();

    rwlock.ReadUnLock(readerNum);
    }
    };
    }

    //Lock class
    class ReadWriteLock {
    private int readerCount;
    private Semaphore mutex;
    private Semaphore rwlock;

    public ReadWriteLock() {
    readerCount = 0;
    mutex = new Semaphore(1);
    rwlock = new Semaphore(1);
    }

    public void ReadLock(int readerNum) {
    try{
    mutex.acquire();
    }
    catch (InterruptedException e) {

    }
    ++readerCount;


    if (readerCount == 1){
    try{
    rwlock.acquire();
    }
    catch (InterruptedException e) {

    }
    }

    System.out.println("Reader " + readerNum + " is reading. Reader count = " + readerCount);
    mutex.release();
    }

    public void ReadUnLock(int readerNum) {
    try{
    mutex.acquire();
    }
    catch (InterruptedException e) {}

    --readerCount;

    if (readerCount == 0){
    rwlock.release();
    }

    System.out.println("Reader " + readerNum + " is done reading. Reader count = " + readerCount);

    mutex.release();
    }

    public void WriteLock(int writerNum) {
    try{
    rwlock.acquire();
    }
    catch (InterruptedException e) {}
    System.out.println("Writer " + writerNum + " is writing.");
    }

    public void WriteUnLock(int writerNum) {
    System.out.println("Writer " + writerNum + " is done writing.");
    rwlock.release();
    }
    }
    class SleepUtilities
    {
    public static void nap() {
    nap(NAP_TIME);
    }

    public static void nap(int duration) {
    int sleeptime = (int) (NAP_TIME * Math.random() );
    try { RW.sleep(sleeptime*1000); }
    catch (InterruptedException e) {}
    }

    private static final int NAP_TIME = 5;
    }

  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Reader Writer Project

    hese are my errors:
    The constructor Writer(ReadWriteLock) is undefined
    The constructor Reader(ReadWriteLock) is undefined
    The compiler can not find a definition for the constructors shown in the error messages that take the arguments. Make sure there is a matching constructor in the class
    or do not use the argument when calling the constructor.

    Please edit your post and wrap your code with code tags:

    [code]
    **YOUR CODE GOES HERE**
    [/code]

    to get highlighting and preserve formatting.
    If you don't understand my answer, don't ignore it, ask a question.

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