Examples of java.util.concurrent.locks.ReentrantReadWriteLock

java.util.concurrent.locks.ReentrantReadWriteLock
release read lock before acquiring write lock rwl.readLock().unlock(); rwl.writeLock().lock(); try { // Recheck state because another thread might have // acquired write lock and changed state before we did. if (!cacheValid) { data = ... cacheValid = true; } // Downgrade by acquiring read lock before releasing write lock rwl.readLock().lock(); } finally { rwl.writeLock().unlock(); // Unlock write, still hold read } } try { use(data); } finally { rwl.readLock().unlock(); } } }} ReentrantReadWriteLocks can be used to improve concurrency in some uses of some kinds of Collections. This is typically worthwhile only when the collections are expected to be large, accessed by more reader threads than writer threads, and entail operations with overhead that outweighs synchronization overhead. For example, here is a class using a TreeMap that is expected to be large and concurrently accessed.
```
  {@code}class RWDictionary  private final Map m = new TreeMap(); private final ReentrantReadWriteLock rwl = new ReentrantReadWriteLock(); private final Lock r = rwl.readLock(); private final Lock w = rwl.writeLock(); public Data get(String key) { r.lock(); try { return m.get(key); } finally { r.unlock(); } } public String[] allKeys() { r.lock(); try { return m.keySet().toArray(); } finally { r.unlock(); } } public Data put(String key, Data value) { w.lock(); try { return m.put(key, value); } finally { w.unlock(); } } public void clear() { w.lock(); try { m.clear(); } finally { w.unlock(); } } }}
```
Implementation Notes

This lock supports a maximum of 65535 recursive write locks and 65535 read locks. Attempts to exceed these limits result in {@link Error} throws from locking methods. @since 1.5 @author Doug Lea

            if (beanContext.isBeanManagedConcurrency()){
                // Bean-Managed Concurrency
                lock = new BeanManagedLock();
            } else {
                // Container-Managed Concurrency
                lock = new ReentrantReadWriteLock();
            }


            return new Instance(context.getBean(), context.getInterceptors(), context.getCreationalContext(), lock);
        } catch (Throwable e) {
            if (e instanceof java.lang.reflect.InvocationTargetException) {

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          .log(POILogger.WARN, "The close() method is intended to SAVE a package. This package is open in READ ONLY mode, use the revert() method instead !");
      return;
    }


    // Save the content
    ReentrantReadWriteLock l = new ReentrantReadWriteLock();
    try {
      l.writeLock().lock();
      if (this.originalPackagePath != null
          && !"".equals(this.originalPackagePath.trim())) {
        File targetFile = new File(this.originalPackagePath);
        if (!targetFile.exists()
            || !(this.originalPackagePath
                .equalsIgnoreCase(targetFile.getAbsolutePath()))) {
          // Case of a package created from scratch
          save(targetFile);
        } else {
          closeImpl();
        }
      } else if (this.output != null) {
        save(this.output);
      }
    } finally {
      l.writeLock().unlock();
    }


    // Clear
    this.contentTypeManager.clearAll();

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    public ProvidersRegistry(LifecycleManagersRegistry factoryRegistry,
                             ApplicationValidator applicationValidator) {
        this.factoryFactoryRegistry = factoryRegistry;
        this.applicationValidator = applicationValidator;
        ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
        readersLock = readWriteLock.readLock();
        writersLock = readWriteLock.writeLock();
    }

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                            ApplicationValidator applicationValidator) {
        this.applicationValidator = applicationValidator;
        rootResources = new LinkedList<ResourceRecord>();
        dirty = false;
        resourceRecordsFactory = new ResourceRecordFactory(factoryRegistry);
        ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
        readersLock = readWriteLock.readLock();
        writersLock = readWriteLock.writeLock();
    }

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                if (deploymentInfo.isBeanManagedConcurrency()){
                    // Bean-Managed Concurrency
                    lock = new BeanManagedLock();
                } else {
                    // Container-Managed Concurrency
                    lock = new ReentrantReadWriteLock();
                }


                data.instance = new Instance(bean, interceptorInstances, lock);
            } catch (Throwable e) {
                if (e instanceof java.lang.reflect.InvocationTargetException) {

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    public ResourceRegistry(LifecycleManagersRegistry factoryRegistry,
                            ApplicationValidator applicationValidator) {
        this.applicationValidator = applicationValidator;
        rootResources = new LinkedList<ResourceRecord>();
        resourceRecordsFactory = new ResourceRecordFactory(factoryRegistry);
        ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
        readersLock = readWriteLock.readLock();
        writersLock = readWriteLock.writeLock();
        uriToResourceCache.put(Boolean.TRUE,
                               new SoftConcurrentMap<String, ArrayList<ResourceRecord>>());
        uriToResourceCache.put(Boolean.FALSE,
                               new SoftConcurrentMap<String, ArrayList<ResourceRecord>>());
    }

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        if (lifecycleManagerRegistry == null) {
            throw new NullPointerException("lifecycleManagerRegistry");
        }
        this.lifecycleManagerRegistry = lifecycleManagerRegistry;
        this.cacheByClass = new HashMap<Class<?>, ResourceRecord>();
        ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
        readersLock = readWriteLock.readLock();
        writersLock = readWriteLock.writeLock();
    }

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        else
        {
            if ( rwLock == null )
            {
                // Create a ReadWrite lock from scratch
                rwLock = new ReentrantReadWriteLock();
            }
        }
    }

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      lockSegmentMask = numLocks - 1;


      sharedLocks = new ReentrantReadWriteLock[numLocks];


      for (int i = 0; i < numLocks; i++) {
        sharedLocks[i] = new ReentrantReadWriteLock();
    }
   }

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    * Blocks until a lock is acquired.
    *
    * @param exclusive if true, a write (exclusive) lock is attempted, otherwise a read (shared) lock is used.
    */
   public void acquireLock(Object key, boolean exclusive) {
      ReentrantReadWriteLock lock = getLock(key);
      if (exclusive) {
         lock.writeLock().lock();
         if (trace) log.tracef("WL acquired for '%s'", key);
      } else {
         lock.readLock().lock();
         if (trace) log.tracef("RL acquired for '%s'", key);
      }
   }

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Examples of java.util.concurrent.locks.ReentrantReadWriteLock

Implementation Notes

Related Classes of java.util.concurrent.locks.ReentrantReadWriteLock