题解 | 字符串排序

import java.util.ArrayList;
import java.util.Comparator;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String line = in.nextLine();
        char[] arr = line.toCharArray();
        ArrayList<Character> list = new ArrayList<>();
        for (char c : arr) {
            if (Character.isLetter(c)){
                list.add(c);
            }
        }
        list.sort(new Comparator<Character>() {
            @Override
            public int compare(Character o1, Character o2) {
                return Character.toLowerCase(o1) - Character.toLowerCase(o2);

            }
        });
        StringBuilder sb = new StringBuilder();
        int j = 0;
        for (int i = 0; i < arr.length; i++) {
            char c = arr[i];
            if (Character.isLetter(c)){
                sb.append(list.get(j++));
            }else {
                sb.append(c);
            }
        }
        System.out.println(sb);
    }
}