题解 | #字符串排序#

import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

// 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);

        String l = in.nextLine();

        char[] c =  l.toCharArray();
        List<Character> letters = new ArrayList<>();
        List<Character> noLetters = new ArrayList<>();
        for (int i = 0 ; i < c.length; i++) {
            if ((c[i] < 'a' || c[i] > 'z') && (c[i] < 'A' || c[i] > 'Z') ) {
                noLetters.add(c[i]);
            } else {
                letters.add(c[i]);
            }
        }

        letters.sort(new Comparator<Character>() {
            @Override
            public int compare(Character o1, Character o2) {
                return Character.toLowerCase(o1) - Character.toLowerCase(o2);
            }
        });

        // 排好序了 接下来把后面的插入进去
        StringBuilder sb = new StringBuilder();

        for (int i = 0 ,j=0; i < c.length; i++) {
            if ((c[i] < 'a' || c[i] > 'z') && (c[i] < 'A' || c[i] > 'Z') ) {
                sb.append(c[i]);
            } else {
                sb.append(letters.get((j++)));
            }
        }
        System.out.println(sb.toString());
    }
}