In this test there is a loop

                long pos = 0L;
                for (;;) {
                    bb.clear();
                    int n = fc.read(bb, pos);
                    if (n > 0)
                        pos += n;
                    // fc.size is important here as it is position sensitive
                    if (pos > fc.size()) // incorrect relational operator: should be >=
                        pos = 0L;
                }

which is supposed to read continuously from a FileChannel. This will not happen however because the value of pos will reach fc.size() which is 1024*1024 + 1 and remain there for all subsequent iterations of the loop in which case fc.read() would no longer read any bytes. The relational operator ">" should be changed to ">=".