code: static void release(BufferPool.Buffer buff) throws IOException {
      if (buff.buf.length == staticConf.getSmallBufferSize()) {
        smallBufferPool.put(buff);
      } else if (buff.buf.length == staticConf.getMediumBufferSize()) {
        mediumBufferPool.put(buff);
      } else if (buff.buf.length == staticConf.getLargeBufferSize()) {
        largeBufferPool.put(buff);
      }
    }
docs: Release a buffer back to the pool. MUST be called to gain the
  benefit of pooling.
  
  @param buff - the buffer
  @throws java.io.IOException