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 ResizablePersistentIntBuffer(File f, int size) throws IOException {
    this.filename = f;
    isNew = !f.exists();
    this.raf = new RandomAccessFile(f, "rw");
    this.lock = new ReentrantReadWriteLock();
    this.size = size;
    buffer = new int[size];
    long expectedLength = ((long)size)*4;
    long realLength = raf.length();
    if(realLength > expectedLength)

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  protected final int length;


  protected transient ReadWriteLock lock = new ReentrantReadWriteLock();
  
  public void init() {
    lock = new ReentrantReadWriteLock();
  }

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     *              will be towards newer values
     * @param clock the clock used to timestamp samples and track rescaling
     */
    public ExponentiallyDecayingReservoir(int size, double alpha, Clock clock) {
        this.values = new ConcurrentSkipListMap<Double, WeightedSample>();
        this.lock = new ReentrantReadWriteLock();
        this.alpha = alpha;
        this.size = size;
        this.clock = clock;
        this.count = new AtomicLong(0);
        this.startTime = currentTimeInSeconds();

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    for(int i = 0; i < NUM_TESTS; i++){
      
      new Thread(new Runnable(){
        
        
        private final ReadWriteLock rwl = new ReentrantReadWriteLock();


        @Override
        public void run() {
          Random rand= new Random();
          int min = 700, max = 10000;
          int randomNum = rand.nextInt(max - min + 1) + min;
        // try and throw threads of sequential access  
           try {
            Thread.sleep(randomNum);
          } catch (InterruptedException e) {
            e.printStackTrace();
          }
          
          Lock rl = rwl.writeLock();
          rl.lock();
          atom.incrementAndGet();
          rl.unlock();
          
          Lock wl = rwl.readLock();
          wl.lock();
          System.out.println("threadId "+threadId +"lockOblect state "+atom.get());
          
          wl.unlock();
          threadId++;

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    /**
     * {@inheritDoc}
     */
    public ReadWriteLock getRWLock()
    {
        return new ReentrantReadWriteLock();
    }

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    this.user = user;
    this.appId = appId;
    this.credentials = credentials;
    this.aclsManager = context.getApplicationACLsManager();
    this.context = context;
    ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
    readLock = lock.readLock();
    writeLock = lock.writeLock();
    stateMachine = stateMachineFactory.make(this);
  }

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    this.committer = committer;
    this.newApiCommitter = newApiCommitter;


    this.taskAttemptListener = taskAttemptListener;
    this.eventHandler = eventHandler;
    ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    this.readLock = readWriteLock.readLock();
    this.writeLock = readWriteLock.writeLock();


    this.jobCredentials = jobCredentials;
    this.jobTokenSecretManager = jobTokenSecretManager;


    this.aclsManager = new JobACLsManager(conf);

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    // Initialize reportedStatus
    reportedStatus = new TaskAttemptStatus();
    initTaskAttemptStatus(reportedStatus);


    ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    readLock = readWriteLock.readLock();
    writeLock = readWriteLock.writeLock();


    this.credentials = credentials;
    this.jobToken = jobToken;
    this.eventHandler = eventHandler;
    this.jobFile = jobFile;

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

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


            // load the last stored valid CSN value
            String contextEntryId = getEntryId( getSuffixDn() );

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Examples of java.util.concurrent.locks.ReentrantReadWriteLock

Implementation Notes

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