#vulnerable code 
                                @Override
    public void readComplete(int rc, LedgerHandle lh, Enumeration<LedgerEntry> seq, Object ctx) {
        // get back to prev value
        lh.lastAddConfirmed--;
        if (rc == BKException.Code.OK) {
            LedgerEntry entry = seq.nextElement();
            byte[] data = entry.getEntry();

            /*
             * We will add this entry again to make sure it is written to enough
             * replicas. We subtract the length of the data itself, since it will
             * be added again when processing the call to add it.
             */
            synchronized (lh) {
                lh.length = entry.getLength() - (long) data.length;
            }
            lh.asyncRecoveryAddEntry(data, 0, data.length, this, null);
            return;
        }

        if (rc == BKException.Code.NoSuchEntryException || rc == BKException.Code.NoSuchLedgerExistsException) {
            lh.asyncCloseInternal(new CloseCallback() {
                @Override
                public void closeComplete(int rc, LedgerHandle lh, Object ctx) {
                    if (rc != KeeperException.Code.OK.intValue()) {
                        LOG.warn("Close failed: " + BKException.getMessage(rc));
                        cb.operationComplete(BKException.Code.ZKException, null);
                    } else {
                        cb.operationComplete(BKException.Code.OK, null);
                        LOG.debug("After closing length is: {}", lh.getLength());
                    }
                }
                }, null, BKException.Code.LedgerClosedException);
            return;
        }

        // otherwise, some other error, we can't handle
        LOG.error("Failure " + BKException.getMessage(rc) + " while reading entry: " + (lh.lastAddConfirmed + 1)
                  + " ledger: " + lh.ledgerId + " while recovering ledger");
        cb.operationComplete(rc, null);
        return;
    } 
                            #location 4 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public void readComplete(int rc, LedgerHandle lh, Enumeration<LedgerEntry> seq, Object ctx) {
        if (rc == BKException.Code.OK) {
            LedgerEntry entry = seq.nextElement();
            byte[] data = entry.getEntry();

            /*
             * We will add this entry again to make sure it is written to enough
             * replicas. We subtract the length of the data itself, since it will
             * be added again when processing the call to add it.
             */
            synchronized (lh) {
                lh.length = entry.getLength() - (long) data.length;
            }
            lh.asyncRecoveryAddEntry(data, 0, data.length, this, null);
            return;
        }

        if (rc == BKException.Code.NoSuchEntryException || rc == BKException.Code.NoSuchLedgerExistsException) {
            lh.asyncCloseInternal(new CloseCallback() {
                @Override
                public void closeComplete(int rc, LedgerHandle lh, Object ctx) {
                    if (rc != KeeperException.Code.OK.intValue()) {
                        LOG.warn("Close failed: " + BKException.getMessage(rc));
                        cb.operationComplete(BKException.Code.ZKException, null);
                    } else {
                        cb.operationComplete(BKException.Code.OK, null);
                        LOG.debug("After closing length is: {}", lh.getLength());
                    }
                }
                }, null, BKException.Code.LedgerClosedException);
            return;
        }

        // otherwise, some other error, we can't handle
        LOG.error("Failure " + BKException.getMessage(rc) + " while reading entry: " + (lh.lastAddConfirmed + 1)
                  + " ledger: " + lh.ledgerId + " while recovering ledger");
        cb.operationComplete(rc, null);
        return;
    }