题解 | #字符串排序#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String  a = in.nextLine();
            char[] cArr = a.toCharArray();
            List<Character> cList = new ArrayList<>();
            Map<Integer,Character> notLetterMap=new HashMap<>();
            for (int i = 0; i < a.length(); i++) {
                char cCur = cArr[i];
                //不是字母存在hashMap中
                if (!isLetter(cCur)) {
                    notLetterMap.put(i,cCur);
                    continue;
                }
                //是字母
                //第一个字母无需比较
                if (cList.isEmpty()) {
                    cList.add(cCur);
                    continue;
                }
                //子循环中cList不存放非字符
                for (int j = 0; j < cList.size(); j++) {
                    char cListCur = cList.get(j);
                    //例子cCur='a' cList.get(j)='b' 将a放在cList的当前位置b往后顺延
                    if (letterDiff(cCur, cListCur) < 0) {
                        cList.add(j, cCur);
                        //值放入跳出子循环
                        break;
                    }
                    //例子cCur='b' cList.get(j)='a' 往后顺延
                    if (letterDiff(cCur, cListCur) > 0) {
                        if (j == cList.size() - 1) {
                            cList.add(cList.size(), cCur);
                            break;
                        }
                        continue;
                    }

                    if (isSameLetter(cCur, cListCur)) {
                        if (j == cList.size() - 1) {
                            cList.add(cList.size(), cCur);
                            break;
                        }
                        continue;
                    }



                }

            }
            notLetterMap.keySet().stream().sorted().forEach(i->cList.add(i,notLetterMap.get(i)));
            cList.forEach(s->System.out.print(s));



        }

    }
    static int letterDiff(char a, char b) {
        return Character.toLowerCase(a) - Character.toLowerCase(b);
    }
    static boolean isSameLetter(char a, char b) {
        return letterDiff(a, b) == 0;
    }
    static boolean isLetter(char c) {
        return (c >= 'a' && c <='z') || (c >= 'A' && c <= 'Z');
    }
}