#vulnerable code 
                                public boolean commitAt(long firstLogIndex, long lastLogIndex, PeerId peer) {
        //TODO  use lock-free algorithm here?
        final long stamp = stampedLock.writeLock();
        long lastCommittedIndex = 0;
        try {
            if (pendingIndex == 0) {
                return false;
            }
            if (lastLogIndex < pendingIndex) {
                return true;
            }

            if (lastLogIndex >= pendingIndex + pendingMetaQueue.size()) {
                throw new ArrayIndexOutOfBoundsException();
            }

            final long startAt = Math.max(pendingIndex, firstLogIndex);
            Ballot.PosHint hint = new Ballot.PosHint();
            for (long logIndex = startAt; logIndex <= lastLogIndex; logIndex++) {
                final Ballot bl = this.pendingMetaQueue.get((int) (logIndex - pendingIndex));
                hint = bl.grant(peer, hint);
                if (bl.isGranted()) {
                    lastCommittedIndex = logIndex;
                }
            }
            if (lastCommittedIndex == 0) {
                return true;
            }
            // When removing a peer off the raft group which contains even number of
            // peers, the quorum would decrease by 1, e.g. 3 of 4 changes to 2 of 3. In
            // this case, the log after removal may be committed before some previous
            // logs, since we use the new configuration to deal the quorum of the
            // removal request, we think it's safe to commit all the uncommitted
            // previous logs, which is not well proved right now
            for (long index = pendingIndex; index <= lastCommittedIndex; index++) {
                pendingMetaQueue.pollFirst();
                LOG.debug("Committed log index={}", index);
            }
            pendingIndex = lastCommittedIndex + 1;
            this.lastCommittedIndex = lastCommittedIndex;
        } finally {
            stampedLock.unlockWrite(stamp);
        }
        this.waiter.onCommitted(lastCommittedIndex);
        return true;
    } 
                            #location 37 
                            #vulnerability type INTERFACE_NOT_THREAD_SAFE
#fixed code
                                public boolean commitAt(long firstLogIndex, long lastLogIndex, PeerId peer) {
        //TODO  use lock-free algorithm here?
        final long stamp = stampedLock.writeLock();
        long lastCommittedIndex = 0;
        try {
            if (pendingIndex == 0) {
                return false;
            }
            if (lastLogIndex < pendingIndex) {
                return true;
            }

            if (lastLogIndex >= pendingIndex + pendingMetaQueue.size()) {
                throw new ArrayIndexOutOfBoundsException();
            }

            final long startAt = Math.max(pendingIndex, firstLogIndex);
            Ballot.PosHint hint = new Ballot.PosHint();
            for (long logIndex = startAt; logIndex <= lastLogIndex; logIndex++) {
                final Ballot bl = this.pendingMetaQueue.get((int) (logIndex - pendingIndex));
                hint = bl.grant(peer, hint);
                if (bl.isGranted()) {
                    lastCommittedIndex = logIndex;
                }
            }
            if (lastCommittedIndex == 0) {
                return true;
            }
            // When removing a peer off the raft group which contains even number of
            // peers, the quorum would decrease by 1, e.g. 3 of 4 changes to 2 of 3. In
            // this case, the log after removal may be committed before some previous
            // logs, since we use the new configuration to deal the quorum of the
            // removal request, we think it's safe to commit all the uncommitted
            // previous logs, which is not well proved right now
            pendingMetaQueue.removeRange(0, (int) (lastCommittedIndex - pendingIndex) + 1);
            LOG.debug("Committed log fromIndex={}, toIndex={}.", pendingIndex, lastCommittedIndex);
            pendingIndex = lastCommittedIndex + 1;
            this.lastCommittedIndex = lastCommittedIndex;
        } finally {
            stampedLock.unlockWrite(stamp);
        }
        this.waiter.onCommitted(lastCommittedIndex);
        return true;
    }