#vulnerable code 
                                @Override
    public void readComplete(int rc, LedgerHandle lh, Enumeration<LedgerEntry> seq, Object ctx) {
        if (rc != 0)
            fail("Failed to write entry");
        ls = seq;
        synchronized (sync) {
            sync.value = true;
            sync.notify();
        }

    } 
                            #location 6 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public void readComplete(int rc, LedgerHandle lh, Enumeration<LedgerEntry> seq, Object ctx) {
        SyncObj x = (SyncObj) ctx;
        if (rc != 0) {
            LOG.error("Failure during add {}", rc);
            x.failureOccurred = true;
        }
        synchronized (x) {
            x.value = true;
            x.ls = seq;
            x.notify();
        }
    }