[Demonstration 1]

[Buggy Method]
public void quarantineBookie(BookieSocketAddress bookie) {
    if (quarantinedBookies.getIfPresent(bookie) == null) {
        quarantinedBookies.put(bookie, BOOLEAN);
        logger.warn("Bookie {} has been quarantined because of read/write errors.", bookie);
    }
}

[Buggy Hunk]
quarantinedBookies.put(bookie, BOOLEAN);

[Patch]
quarantinedBookies.put(bookie, Boolean.TRUE);