Java快乐API编程

拿到s后直接转char数组，然后sort完在StringBuffer里面拼接起来，输出即可

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        while(sc.hasNext()) {
            String s = sc.nextLine();
            int len=s.length();
            char[] arr = s.toCharArray();
            Arrays.sort(arr);
            StringBuffer sb=new StringBuffer();
            for(int i=0;i<len;i++){
                sb.append(arr[i]);
            }
            System.out.println(sb);
        }
    }
}