Avoiding multiple lock attempts java

Question

I have the following method:

public foo bar(String id) {
    Lock localLock = lockUtil.lock(id);
    try {
        do something;
        return foo;
    } finally {
        lock.unlock();
    }
}

I need to override this method to take in another parameter.

public foo bar(String id, Integer index) {
    Lock localLock = lockUtil.lock(id);
    try {
        do something with index;
    } finally {
        lock.unlock();
    }

    return bar(id);
}

My question is, how can do achieve this without obtaining the locks twice (in case the second method is called)? I don't want to change the signature of the original method, since that would mean making changes at 10 different places in the system. I'd appreciate any ideas. I can give more clarification regarding the question, if required. Thanks.