如何使用流对不在索引范围内的元素做一件事，对在范围内的元素做另一件事？

Question

这个问题

one two three four five six seven eight

one two THREE FOUR FIVE SIX seven eight

我不喜欢它如何改变数组的位置，以及它如何需要两个流。有更好的办法吗？

import static java.util.stream.Collectors.joining;

import java.util.Arrays;
import java.util.stream.IntStream;

public class UpperCaseElementsInIndexRangeViaIntStream {

   public static void main(String[] ignored) {
      final String input = "one two three four five six seven eight";
      final int MIN_IDX = 2;
      final int MAX_IDX = 5;
      final String[] splits = input.split(" ");

      //Filter only those in range

      String output = IntStream.range(0, splits.length).
            filter(idx -> MIN_IDX <= idx && idx <= MAX_IDX).
            mapToObj(i -> splits[i]).
            collect(joining(" "));

      System.out.println(output);

      //Change the array in place, capitalizing only those in range

      IntStream.range(0, splits.length).forEach(idx -> {
         final String split = splits[idx];
         splits[idx] = (MIN_IDX <= idx && idx <= MAX_IDX)
                       ? split.toUpperCase() : split;
      });

      output = Arrays.stream(splits).collect(joining(" "));

      System.out.println(output);
   }
}

产出：

three four five six
one two THREE FOUR FIVE SIX seven eight

Answer 1

下面是一个没有stream的解决方案。使用子列表以列表的形式获取所需范围的视图。然后使用ReplaceAll就地转换元素。

List<String> all = Arrays.asList(splits);
all.subList(MIN_IDX, MAX_IDX + 1).replaceAll(String::toUpperCase);
// use 'all' as needed

注意，ReplaceAll的第二个参数是独占索引值。