Your code says:
mList.sort(comparing);
I believe you've misunderstood what you've been asked to do - assuming that "use binary search if sorted otherwise use linear search", the title of your question, is what you are supposed to do. You are not supposed to sort them at all. This problem requires no knowledge of how to sort things in Java whatsoever.
What you need to understand is searching, not sorting. And how to check whether a sequence of inputs is already sorted.
Now, admittedly, technically you can check if a sequence is already sorted by actually sorting it and then checking if the resulting sequence is in the same order as what you started with. But I wouldn't recommend that.
What I would recommend, instead, is using a Comparator to compare each pair of adjacent elements (if any) in the sequence, to check if the sequence is monotonically increasing or monotonically decreasing.