1．写一种函数，例如：给你旳 a b c 则输出 abc acb bac bca cab cba package test;import java.util.ArrayList;import java.util.List;public class ListOpreation {public static void main(String[] args){String s = "ABCD";List list = list(s,"");System.out.println(list.size());System.out.println(list);}public static List list(String base,String buff){List result = new ArrayList();if(base.length()<=0){result.add(buff);System.out.println(result.toString()+"&");}for(int i=0;i temp = list(new StringBuilder(base).deleteCharAt(i).toString(),buff+base.charAt(i));result.addAll(temp);}for(int i=0;i
