Probleme und Lösungen für das Multi-Thread-Starvation-Phänomen in Java

In diesem Artikel werden hauptsächlich relevante Informationen zur Lösung des Java-Multi-Thread-Problems vorgestellt. Freunde, die sie benötigen, können darauf zurückgreifen.

So lösen Sie das Problem des Java-Multi-Thread-Problems

Wenn ein Thread liest, darf der schreibende Thread nicht schreiben, aber andere lesende Threads dürfen lesen. Während ein schreibender Thread schreibt, sollten andere Threads nicht lesen oder schreiben. Um zu verhindern, dass der Schreibthread verhungert, sollte beim Lesen des Threads dem nachfolgenden Lesethread das Lesen untersagt werden, wenn der Schreibthread eine Schreibanforderung anfordert.

Der Implementierungscode lautet wie folgt:

File.Java

package readerWriter; 
 
public class File { 
private String name; 
public File(String name) 
{ 
  this.name=name; 
   
} 
}

Pool.java

package readerWriter; 
 
public class Pool { 
private int readerNumber=0; 
private int writerNumber=0; 
private boolean waittingWriten; 
 
public boolean isWaittingWriten() { 
  return waittingWriten; 
} 
public void setWaittingWriten(boolean waittingWriten) { 
  this.waittingWriten = waittingWriten; 
} 
 
 
 
public File getFile() { 
  return file; 
} 
public void setFile(File file) { 
  this.file = file; 
} 
File file; 
public Pool(File file) 
{ 
  this.file=file; 
 
} 
public int getReaderNumber() { 
  return readerNumber; 
} 
public void setReaderNumber(int readerNumber) { 
  this.readerNumber = readerNumber; 
} 
public int getWriterNumber() { 
  return writerNumber; 
} 
public void setWriterNumber(int writerNumber) { 
  this.writerNumber = writerNumber; 
} 
 
}

Reader.java

package readerWriter; 
 
public class Reader implements Runnable{ 
   
  private String id; 
  private Pool pool; 
   
   
  public Reader(String id,Pool pool) 
  { 
    this.id=id; 
    this.pool=pool; 
  } 
   
   
  @Override 
  public void run() 
  { 
    // TODO Auto-generated method stub 
    while(!Thread.currentThread().interrupted()){ 
       
    synchronized(pool){ 
       
        while(pool.getWriterNumber()>0 || pool.isWaittingWriten()==true)//当线程正在写或者 
                                        //有线程正在等待写，则禁止读线程继续读  
        { 
           
             
              try { 
                pool.wait(); 
              } catch (InterruptedException e) { 
                // TODO Auto-generated catch block 
                e.printStackTrace(); 
              } 
             
           
           
        } 
       
      { 
         
        pool.setReaderNumber(pool.getReaderNumber()+1);  
          
         
      } 
    } 
     System.out.println(id+" "+"is reading...."); 
      
     try { 
      Thread.sleep(1000); 
    } catch (InterruptedException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } 
   
    synchronized(pool) 
    { 
      pool.setReaderNumber(pool.getReaderNumber()-1);  
      System.out.println(id+"  "+"is existing the reader...."); 
      if(pool.getReaderNumber()==0) 
          pool.notifyAll(); 
    } try { 
      Thread.sleep(1000); 
    } catch (InterruptedException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } 
    // pool.notifyAll(); 
     
      
      
  } 
      
       
   
     
     
  } 
   
 
}

Writer.java

package readerWriter; 
 
public class Writer implements Runnable{ 
  private Pool pool; 
  String id; 
  public Writer(String id,Pool pool) 
  { 
    this.id=id; 
    this.pool=pool; 
     
     
  } 
  @Override 
  public void run() { 
    // TODO Auto-generated method stub 
    while(!Thread.currentThread().interrupted()){ 
       
    synchronized(pool){ 
      if(pool.getReaderNumber()>0) 
        pool.setWaittingWriten(true); 
      else 
        pool.setWaittingWriten(false); 
     
      //当线程正在被读或者被写或者有线程等待读 
       
        while(pool.getWriterNumber()>0 ||  pool.getReaderNumber()>0)   
        { 
          try { 
            pool.wait();   
          } catch (InterruptedException e) { 
            // TODO Auto-generated catch block 
            e.printStackTrace(); 
          } 
           
        } 
      pool.setWaittingWriten(false);  //这个策略还算公平 
      { 
         
        pool.setWriterNumber(pool.getWriterNumber()+1); 
          
         
      } 
    } 
     System.out.println(id+" "+"is writing...."); 
 
     try { 
      Thread.sleep(1000); 
    } catch (InterruptedException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
    } 
      
     // 
    synchronized(pool) 
    { 
       
      pool.setWriterNumber(pool.getWriterNumber()-1); 
      System.out.println(id+"  "+"is existing the writer...."); 
      pool.notifyAll(); 
    } 
     /* try { 
        Thread.sleep(1000); 
        //System.out.println("writer sleeping over"); 
      } catch (InterruptedException e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
      } */ 
     
      
      
  } 
 
} 
}

Main.java

package readerWriter; 
 
public class Main { 
 
  public static void main(String[] args) { 
    // TODO Auto-generated method stub 
Pool pool=new Pool(new File("dd file")); 
for(int i=0;i<2;i++) 
{ 
 Thread writer=new Thread(new Writer("writer "+i,pool)); 
 writer.start(); 
} 
for(int i=0;i<5;i++) 
{ 
   
  Thread reader=new Thread(new Reader("reader "+i,pool)); 
  reader.start(); 
   
 
} 
 
 
 
 
  } 
 
}

Das Ergebnis der Ausführung eines Teils des Programms ist wie folgt:

writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
reader 0 is reading.... 
reader 0  is existing the reader.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
reader 3 is reading.... 
reader 2 is reading.... 
reader 4 is reading.... 
reader 1 is reading.... 
reader 0 is reading.... 
reader 3  is existing the reader.... 
reader 1  is existing the reader.... 
reader 0  is existing the reader.... 
reader 4  is existing the reader.... 
reader 2  is existing the reader.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 1 is writing.... 
writer 1  is existing the writer.... 
reader 2 is reading.... 
reader 2  is existing the reader.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing.... 
writer 0  is existing the writer.... 
writer 0 is writing....

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