Create and find highest value in subarraylist-CodePudding

I have an Arraylist of the Cells from an Excel sheet. I want to create subarraylists of size 50 from the Arraylist of Cells I actually have, beginning from the index of 1590 and ending with size()-700.

I want to get the highest number from every subarraylist and put it in the new Arraylist. in the new Arraylist there should be only the highest values of each subarraylist.

Input data is my Arraylist of Cells.

With this code I get more than 50 numbers and it's not always the highest value. Has anyone an idea?

This is my code:

int partitionSize = 50;

List<List<Cell>> partitions = new ArrayList<>();
List <Cell> high = new ArrayList();
Cell max = data.get(1590);

for (int i = 1590; i < data.size()-700; i  = partitionSize) {
    partitions.add(data.subList(i, Math.min(i   partitionSize, data.size()-700)));
}

for (List<Cell> list : partitions) {
    for (int i = 1; i < list.size(); i  ) {
        if (list.get(i).getNumericCellValue() > max.getNumericCellValue()) {
            max = list.get(i);
        }
        high.add(max);
    }
}

CodePudding user response：

You could take advantage of the Stream API.

For example:

List<List<Integer>> partitions = new ArrayList<>();
List<Integer> high = partitions.stream()
    .map(partition -> partition.stream().max(Integer::compareTo))
    .filter(Optional::isPresent)
    .map(Optional::get)
    .collect(Collectors.toList());

CodePudding user response：

The list of partitions may be generated using IntStream::iterate:

int start = 1590;
int end = data.size() - 700;
int size = 50;
List<List<Cell>> partitions = IntStream
    .iterate(start, i -> i < end, i -> i   size) // IntStream
    .mapToObj(i -> data.subList(i, Math.min(i   size, end)))
    .collect(Collectors.toList())
;

Then the list of cells with maximal values can be retrieved as follows:

List<Cell> maxPerRange = partitions
    .stream() // Stream<List<Cell>>
    .map(list -> list.stream() // Stream<Cell>
                     .max(Comparator.comparing(Cell::getNumericCellValue))
                     .get()
    )
    .collect(Collectors.toList());

Similarly, the list of maximal values may be created without explicit splitting the input data in sublists, just by using the appropriate ranges similar to the nested loops:

List<Cell> maxPerRange = IntStream
    .iterate(start, i -> i < end, i -> i   size) // IntStream
    .mapToObj(i -> IntStream.range(i, Math.min(i   size, end))
            .mapToObj(data::get)
            .max(Comparator.comparing(Cell::getNumericCellValue))
            .get()
    )
    .collect(Collectors.toList());