code: @Override
      protected boolean checkBuffer() throws IOException {
          if (null != this.buffer) {
              if (this.buffer.hasRemaining()) {
                  return true;
              }
              this.buffer.release();
              this.buffer = null;
          }
          return setNextBuffer();
      }
docs: /*
  (non-Javadoc)
  
  @see com.ibm.wsspi.http.HttpInputStream#checkBuffer()