private boolean isByteBufferPositionedReadable() {
    try {
      // long position, ByteBuffer buf
      FSDataInputStream.class.getMethod("read", long.class, ByteBuffer.class);
    } catch (NoSuchMethodException e) {
      return false;
    }
    return true;
  }
Determine if ByteBufferPositionedReadable API is available .
@return true if FSDataInputStream implements ByteBufferPositionedReadable API.
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestBlockIOUtils.java