code: public Lease acquire() throws Exception
      {
          Collection<Lease> leases = acquire(1, 0, null);
          return leases.iterator().next();
      }
docs: <p>Acquire a lease. If no leases are available, this method blocks until either the maximum
  number of leases is increased or another client/process closes a lease.</p>
  <p>The client must close the lease when it is done with it. You should do this in a
  <code>finally</code> block.</p>
  
  @return the new lease
  @throws Exception ZK errors, interruptions, etc.