How to sort ArrayList<Long> in decreasing order?

Here's one way for your list:

list.sort(null);
Collections.reverse(list);

Or you could implement your own Comparator to sort on and eliminate the reverse step:

list.sort((o1, o2) -> o2.compareTo(o1));

Or even more simply use Collections.reverseOrder() since you're only reversing:

list.sort(Collections.reverseOrder());

Comparator<Long> comparator = Collections.reverseOrder();
Collections.sort(arrayList, comparator);

You can use the following code which is given below;

Collections.sort(list, Collections.reverseOrder());

or if you are going to use custom comparator you can use as it is given below

Collections.sort(list, Collections.reverseOrder(new CustomComparator());

Where CustomComparator is a comparator class that compares the object which is present in the list.

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