#vulnerable code 
                                public AvProxy bind(String url) {
        if (testUrls.size() < 10) {
            testUrls.add(url);
        } else {
            testUrls.set(random.nextInt(10), url);
        }
        if (needFresh()) {
            refresh();// 在新线程刷新
        }

        readWriteLock.readLock().lock();
        try {
            return smartProxyQueue.getAndAdjustPriority();
        } finally {
            readWriteLock.readLock().unlock();
        }
    } 
                            #location 8 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                public AvProxy bind(String url) {
        if (testUrls.size() < 10) {
            testUrls.add(url);
        } else {
            testUrls.set(random.nextInt(10), url);
        }
        if (needFresh()) {
            refresh();// 在新线程刷新
        }
        return smartProxyQueue.getAndAdjustPriority();
    }