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

   public void readExternal(java.io.ObjectInput in)
      throws java.io.IOException, ClassNotFoundException
   {
      this.guid = (GUID)in.readObject();
      this.timeout = in.readLong();
      this.lock = new ReentrantReadWriteLock();
   }

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    public void tearDown() {
    }


    @Test
    public void testWithLocking() {
        ReentrantReadWriteLock readWriteLock = dhns.getReadWriteLock();
        Lock lock = readWriteLock.readLock();


        for (int i = 0; i < 100000; i++) {
            lock.lock();
            int degree = singleNode.getEdgesInTree().getCount() + singleNode.getEdgesOutTree().getCount();
            lock.unlock();

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        }
    }


    @Test
    public void testWithGlobalLocking() {
        ReentrantReadWriteLock readWriteLock = dhns.getReadWriteLock();
        Lock lock = readWriteLock.readLock();


        lock.lock();
        for (int i = 0; i < 100000; i++) {
            lock.lock();
            int degree = singleNode.getEdgesInTree().getCount() + singleNode.getEdgesOutTree().getCount();

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    public void readUnlock() {
        readWriteLock.readLock().unlock();
    }


    public void readUnlockAll() {
        ReentrantReadWriteLock lock = readWriteLock;
        final int nReadLocks = lock.getReadHoldCount();
        for (int n = 0; n < nReadLocks; n++) {
            lock.readLock().unlock();
        }
    }

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        if (lifecycleManagerRegistry == null) {
            throw new NullPointerException("lifecycleManagerRegistry"); //$NON-NLS-1$
        }
        this.lifecycleManagerRegistry = lifecycleManagerRegistry;
        this.cacheByClass = new HashMap<Class<?>, ResourceRecord>();
        ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
        readersLock = readWriteLock.readLock();
        writersLock = readWriteLock.writeLock();


        if (customProperties == null) {
            customProperties = new Properties();
        }

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    _readWrite = new BlockReadWrite(this, path, isEnableMmap);


    _writer = new BlockWriter(this);


    if (rowLock == null)
      rowLock = new ReentrantReadWriteLock();


    rowLock.readLock();
    _rowWriteLock = rowLock.writeLock();
  }

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    _store = store;
    _blockId = blockId;


    // _lock = new Lock("block:" + store.getName() + ":" + Long.toHexString(_blockId));
    // ReadWriteLock rwLock = new ReentrantReadWriteLock();
    ReadWriteLock rwLock = new ReentrantReadWriteLock();
    
    _readLock = rwLock.readLock();
    _writeLock = rwLock.writeLock();


    _isFlushDirtyOnCommit = _store.isFlushDirtyBlocksOnCommit();


    _buffer = allocateBuffer();

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      revert();
      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);
        output.close();
      }
    } finally {
      l.writeLock().unlock();
    }


    // Clear
    this.contentTypeManager.clearAll();
  }

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   *
   * @param region the region to connect to
   */
  public IdxRegionIndexManager(IdxRegion region) {
    this.region = region;
    indexSwitchLock = new ReentrantReadWriteLock();
    heapSize = FIXED_SIZE;
  }

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  protected int crossCatalogResultSortingThreshold;
  
  public CatalogServiceLocal(CatalogRepository catalogRepository, IngestMapper ingestMapper, File pluginStorageDir, TransactionIdFactory transactionIdFactory, boolean restrictQueryPermissions, boolean restrictIngestPermissions, boolean oneCatalogFailsAllFail, boolean simplifyQueries, boolean disableIntersectingCrossCatalogQueries, int crossCatalogResultSortingThreshold) throws InstantiationException {
    try {
      this.catalogs = new HashSet<Catalog>();
      this.catalogsLock = new ReentrantReadWriteLock();
      this.ingestMapperLock = new ReentrantReadWriteLock();
      this.setPluginStorageDir(pluginStorageDir);
      this.setRestrictQueryPermissions(restrictQueryPermissions);
      this.setRestrictIngestPermissions(restrictIngestPermissions);
      this.setTransactionIdFactory(transactionIdFactory);
      this.setIngestMapper(ingestMapper);

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Examples of java.util.concurrent.locks.ReentrantReadWriteLock

Implementation Notes

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