题解 | 字符串排序

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
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);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNext()) { // 注意 while 处理多个 case
            String str = in.nextLine();
            int n = str.length();
            List<Character> list = new ArrayList<Character>();
            char []charS = new char[n];
            for (int i = 0; i < n; i++) {
                if (str.charAt(i) >= 65 && str.charAt(i) <= 90 || str.charAt(i) >= 97 &&
                        str.charAt(i) <= 122) {
                    list.add(str.charAt(i));
                } else {
                    charS[i] = str.charAt(i);
                }
            }
            list.sort((a, b)->Character.toLowerCase(a) - Character.toLowerCase(b));
            int i = 0;
            Iterator it = list.iterator();
            while (i < n) {
                if (charS[i] == 0 && it.hasNext()) {
                    Character c = (Character)it.next();
                    charS[i] = c;
                }
                i++;
            }
            StringBuilder sb = new StringBuilder();
            for (int j = 0; j < n; j++) {
                sb.append(charS[j]);
            }
            System.out.println(sb.toString());

        }
    }
}