@Override
  public long incr(String key, long by, long def) {
    return mutateWithDefault(Mutator.incr, key, by, def, 0);
  }
Increment the given counter, returning the new value.

@param key the key
@param by the amount to increment
@param def the default value (if the counter does not exist)
@return the new value, or -1 if we were unable to increment or add
@throws OperationTimeoutException if the global operation timeout is
          exceeded
@throws IllegalStateException in the rare circumstance where queue is too
          full to accept any more requests
src/main/java/net/spy/memcached/MemcachedClient.java