Читатели-писатели с мониторами - java

Question

Я внедряю проблемы писателей-писателей с мониторами на Java. Есть много читателей и писателей. Когда писатель пишет, ни один читатель или писатель не может читать или писать. Многие читатели могут читать одновременно. Я не знаю, что не так с этим кодом. Существует проблема взаимоблокировки.

class Monitor { 
    private int readers; // specifies number of readers reading 
    private boolean writing; // specifies if someone is writing 
    private Condition OK_to_Read, OK_to_Write; 

    public Monitor() { 
     readers = 0; 
     writing = false; 
     OK_to_Read = new Condition(); 
     OK_to_Write = new Condition(); 
    } 

    public synchronized void Start_Read(int n) { 

     System.out.println("wants to read " + n); 
     if (writing || OK_to_Write.is_non_empty()) { 
      try { 
       System.out.println("reader is waiting " + n); 
       OK_to_Read.wait_(); 
      } catch (InterruptedException e) { 
      } 
     } 
     readers += 1; 
     OK_to_Read.release_all(); 

    } 

    public synchronized void End_Read(int n) { 

     System.out.println("finished reading " + n); 
     readers -= 1; 

     if (OK_to_Write.is_non_empty()) { 
      OK_to_Write.release_one(); 
     } else if (OK_to_Read.is_non_empty()) { 
      OK_to_Read.release_one(); 
     } else { 
      OK_to_Write.release_all(); 
     } 

    } 

    public synchronized void Start_Write(int n) { 
     System.out.println("wants to write " + n); 
     if (readers != 0 || writing) { 
      try { 
       System.out.println("Writer is waiting " + n); 
       OK_to_Write.wait_(); 
      } catch (InterruptedException e) { 
      } 
     } 

     writing = true; 

    } 

    public synchronized void End_Write(int n) { 

     System.out.println("finished writing " + n); 
     writing = false; 
     if (OK_to_Read.is_non_empty()) { 
      OK_to_Read.release_one(); 
     } else if (OK_to_Write.is_non_empty()) { 
      OK_to_Write.release_one(); 
     } else { 
      OK_to_Read.release_all(); 
     } 

    } 

} 

class Condition { 
    private int number;// specifies the number of readers/writers waiting 

    public Condition() { 
     number = 0; 
    } 

    public synchronized boolean is_non_empty() { 
     if (number == 0) 
      return false; 
     else 
      return true; 
    } 

    public synchronized void release_all() { 
     number = 0; 
     notifyAll(); 
    } 

    public synchronized void release_one() { 
     number -= 1; 
     notify(); 
    } 

    public synchronized void wait_() throws InterruptedException { 
     number++; 
     wait(); 
    } 

} 

class Reader extends Thread { 
    private Monitor M; 
    private String value; 

    public Reader(String name, Monitor c) { 
     super(name); 
     M = c; 
    } 

    public void run() { 
     for (int i = 0; i < 10; i++) { 
      M.Start_Read(i); 
      // System.out.println("Reader "+getName()+" is retreiving data..."); 
      System.out.println("Reader is reading " + i); 
      M.End_Read(i); 
     } 

    } 
} 

class Writer extends Thread { 
    private Monitor M; 
    private int value; 

    public Writer(String name, Monitor d) { 
     super(name); 
     M = d; 
    } 

    public void run() { 
     for (int j = 0; j < 10; j++) { 
      M.Start_Write(j); 
      // System.out.println("Writer "+getName()+" is writing data..."); 
      System.out.println("Writer is writing " + j); 
      M.End_Write(j); 
     } 

    } 
} 

class mainClass { 
    public static void main(String[] args) { 
     Monitor M = new Monitor(); 
     Reader reader = new Reader("1", M); 
     Writer writer = new Writer("1", M); 
     writer.start(); 
     reader.start(); 
    } 
} 

Answer 1

Я положил sleep метод внутри вашего кода. Пожалуйста, проверьте это &.

class Monitor 
{ 
private volatile int readers; //specifies number of readers reading 
private volatile boolean writing; //specifies if someone is writing 
private volatile Condition OK_to_Read, OK_to_Write; 

public Monitor() 
{ 
    readers = 0; 
    writing = false; 
    OK_to_Read = new Condition(); 
    OK_to_Write = new Condition(); 
} 

public synchronized void Start_Read(int n) 
{ 

    System.out.println("wants to read " + n); 
    if(writing || OK_to_Write.is_non_empty()) 
    { 
     try{ 
      System.out.println("reader is waiting " + n); 
      OK_to_Read.sleep_(); 
     } 
     catch(InterruptedException e){} 
    } 
    readers += 1; 
    OK_to_Read.release_all(); 

} 

public synchronized void End_Read(int n) 
{ 

     System.out.println("finished reading " + n); 
     readers -= 1; 

     if(OK_to_Write.is_non_empty()) 
     { 
      OK_to_Write.release_one(); 
     } 
     else if(OK_to_Read.is_non_empty()) 
     { 
      OK_to_Read.release_one(); 
     } 
     else 
     { 
      OK_to_Write.release_all(); 
     } 

} 

public synchronized void Start_Write(int n) 
{ 
    System.out.println("wants to write " + n); 
    if(readers != 0 || writing) 
    { 
     try{ 
      System.out.println("Writer is waiting " + n); 
      OK_to_Write.sleep_(); 
       }catch(InterruptedException e){} 
    } 

    writing = true; 

} 

public synchronized void End_Write(int n) 
{ 

    System.out.println("finished writing " + n); 
    writing = false; 
    if(OK_to_Read.is_non_empty()) 
    { 
     OK_to_Read.release_one(); 
    } 
    else if(OK_to_Write.is_non_empty()) 
    { 
     OK_to_Write.release_one(); 
    } 
    else 
    { 
     OK_to_Read.release_all(); 
    } 

} 

} 

class Condition 
{ 
private int number;//specifies the number of readers/writers waiting 

public Condition() 
{ 
    number = 0; 
} 

public synchronized boolean is_non_empty() 
{ 
    if(number == 0) 
     return false; 
    else 
     return true; 
} 

public synchronized void release_all() 
{ 
number = 0; 
notifyAll(); 
} 


public synchronized void release_one() 
{ 
number -=1; 
notify(); 
} 

public synchronized void wait_() throws InterruptedException 
{ 
    number++; 
    wait(); 
} 
public synchronized void sleep_() throws InterruptedException 
{ 
    Thread.sleep(1000); 
} 

} 


class Reader extends Thread 
{ 
private Monitor M; 
private String value; 
public Reader(String name,Monitor c) 
{ 
    super(name); 
    M=c; 
} 

public void run() 
{ 
    for(int i = 0; i < 10; i++){ 
      M.Start_Read(i); 
      //System.out.println("Reader "+getName()+" is retreiving data..."); 
      System.out.println("Reader is reading " + i); 
      M.End_Read(i); 
    } 

} 
} 

class Writer extends Thread 
{ 
private Monitor M; 
private int value; 
public Writer(String name, Monitor d) 
{ 
    super(name); 
    M = d; 
} 

public void run() 
{ 
    for(int j = 0; j < 10; j++){ 
      M.Start_Write(j); 
      //System.out.println("Writer "+getName()+" is writing data..."); 
      System.out.println("Writer is writing " + j); 
      M.End_Write(j); 
    } 

} 
} 

public class Demo 
{ 
public static void main(String [] args) 
{ 
    Monitor M = new Monitor(); 
    Reader reader = new Reader("1",M); 
    Writer writer = new Writer("1",M); 
    writer.start(); 
    reader.start();  
} } 

Answer 2

Вы должны получить значение функции wait().

За 10 секунд ожидания:

public synchronized void wait_() throws InterruptedException { 
     number++; 
     wait(10000); 
    } 

Для меня это отлично работает после изменения этого.