@Override
  public OperationFuture<Boolean> delete(String key) {
    return delete(key, 0L);
  }
Delete the given key from the cache.

@param key the key to delete
@return whether or not the operation was performed
@throws IllegalStateException in the rare circumstance where queue is too
          full to accept any more requests
src/main/java/net/spy/memcached/MemcachedClient.java