题解 | #字符串排序#

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;
//写一个比较器就可以了，用LinkedList很方便pop
// 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 s = in.nextLine();
            s = sortStr(s);
            System.out.println(s);
        }
    }

    private static String sortStr(String s){
        List<Character> list = new ArrayList<>();
        for(int i = 0;i<s.length();i++){
            char c = s.charAt(i);
            if(c >= 'a' && c <= 'z'){
                list.add(c);
            }else if(c >= 'A' && c <= 'Z'){
                list.add(c); 
            }
        }
        Collections.sort(list, (c1,c2) -> {
            c1 = Character.toUpperCase(c1);
            c2 = Character.toUpperCase(c2);
            if(c1 == c2){
                return 0;
            }else{
                return c1 - c2;
            }
        });
        StringBuilder sb = new StringBuilder();
        LinkedList<Character> listCopy = new LinkedList(list);
        for(int i = 0;i<s.length();i++){
            char c = s.charAt(i);
            if((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')){
                sb.append(listCopy.pop());
            }else{
                sb.append(c);
            }
        }
        return sb.toString();
    }
}