串中取3个不重复字母

import java.util.*;public class 串中取3个不重复字母 {public static void main(String[] args) {// TODO Auto-generated method stub    Scanner reader=new Scanner(System.in);    String s=reader.nextLine();    ArrayList<Character>  array=new ArrayList<Character>();    char[] c=s.toCharArray();    for(int i=0;i<c.length;i++){    if(array.contains(c[i]))    continue;    else    array.add(c[i]);    }    String ss="";    backtrace(array,0,ss);}public static void backtrace(ArrayList<Character>  array,int count,String s){if(s.length()==3)System.out.println(s);for(int i=count;i<array.size();i++){s+=array.get(i);count=i;backtrace(array,count+1,s);s=s.substring(0,s.length()-1);}}}