题解 | 图片整理

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);
        String line = in.nextLine();
        ArrayList<Character> list = new ArrayList<>();	// 用ArrayList实现排序
        for (int i = 0; i < line.length(); i++) {
            list.add(line.charAt(i));
        }

        list.sort(Character::compareTo);
        for (Character character : list) {
            System.out.print(character);
        }        
    }
}