"Multithreaded Access: Synchronizing Java Threads"
Vol. 7, Issue 1, p. 64

	


Listing 1

public void process (Request req) {
    File file = new File(req.getFileName());
    synchronized (file)  {
       // ... open/modify/close file as per the request parameters...
    }
}


Listing 2

public void process (Request req) {
    File file =  acquireFile( req.getFileName() );
    try {
       synchronized (file) {
          // ... open/modify/close file as per the request parameters...
       }
    }
    finally {
       releaseFile( file );
    }
}


Listing 3

public void process (Request req) {
    File file =  new File( req.getFileName() );
    Object semaphore = acquireSemaphore ( file );
    try {
       synchronized (semaphore) {
          // ... open/modify/close file as per the request parameters...
       }
    }
    finally {
       releaseSemaphore( file );
    }
}


Listing 4

public void methodA(LDAPObject obj) {
    String dn = obj.getDN();
    Object semaphore = acquireSemaphore ( dn );
    try {
       synchronized ( semaphore ) {
          // read/modify/delete object
       }
    }
    finally {
       releaseSemaphore ( dn );
    }
}


Listing 5

public class Monitor {
    private WeakHashMap map = new WeakHashMap() {
       public final Object get(Object key) {
          Object ref = super.get(key);
          Object monitor = ((ref == null) ? null : ((WeakReference)ref).get());
          if (monitor == null) {
             monitor = key;
             put (monitor, new WeakReference(monitor));
          }
          return monitor;
       }
    };
    public synchronized Object get(Object key) {
       return map.get(key);
    }
}


Listing 6

static final Monitor monitor = new Monitor();

public void process (Request req) {
    File file =  new File( req.getFileName() );
    synchronized (monitor.get(file)) {
          // ... open/modify/close file as per the request parameters...
    }
}