#vulnerable code 
                                public void clear() {
        Integer[] identifiers = new Integer[0];
        synchronized(this) {
            identifiers = ids.toArray(new Integer[ids.size()]);
        }
        for (int i=0;i<identifiers.length;i++) {
            unsubscribe(identifiers[i]);
        }
        logStatus();
    } 
                            #location 9 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                public void clear() {
        Integer[] identifiers = null;
        synchronized(ids) {
            identifiers = ids.toArray(new Integer[ids.size()]);
            ids.clear();
        }

        for (int i=0;i<identifiers.length;i++) {
            changeReceiver.unsubscribed(identifiers[i], this);
        }
    }