Java - splice out part of a list, reverse it and overwrite previous part

Question

i would like to know how this task can be done as easy as possible with Java:

1. Splice out a part of an ArrayList (by index)
2. Reverse this splice
3. Overwrite index range from the original list with the spliced/reversed one.

For example, i have a list with these numbers:

[3,2,8,9]

Splice out:

[2,8,9]

reverse it:

[9,8,2]

put it back together:

[3,9,8,2]

Best regards

Answer 1

Here is generic code for your requirement with complexity of O(n) -

<E> List<E> spliceAndReverse(List<E> list, int startIndex, int endIndex){
        while(startIndex < endIndex){
            E e = list.get(startIndex);
            list.set(startIndex, list.get(endIndex));
            list.set(endIndex, e);
            startIndex++;
            endIndex--;
        }   
        return list;
    }

We can also use sublist, here is code for that -

static <E> List<E> spliceAndReverseUsingSubList(List<E> list, int startIndex, int endIndex){
        List<E> subList =  list.subList(startIndex, endIndex+1);
        Collections.reverse(subList);
        List<E> resultList = new ArrayList<>(list.subList(0, startIndex));
        resultList.addAll(subList);
        if(list.size() != endIndex+1){
        resultList.addAll(list.subList(endIndex+1, list.size()));
        }
        return resultList;
    }

See Example here - http://blog.deepaktripathi.in/uncategorized/reverse-arraylist-between-2-given-indexes/

Note - Before asking question on platform please make sure you have tried enough.