public class Pailie2
{
    static List<String> usrInput = new LinkedList<String>();
    static List<String> result = new LinkedList<String>();
    public static void main(String[] args)
    {
  String str = "abcde";
  init(str);
  System.out.println(usrInput.size());
  calc(str.length(),usrInput,"");
  int count = 0;
  for (String elem : result)
  {
      System.out.println(elem);
      count++;
  }
  System.out.println("count:"+count);
    }
    
    //将用户输入的字符串装入到一个usrInput的list里面
    public static void init(String str)
    {
  Set<Character> set = new HashSet<Character>();
  for (int i = 0; i < str.length(); i++)
  {
      set.add(str.charAt(i));
  }
  for (Iterator it = set.iterator(); it.hasNext();)
  {
      Character elem = (Character)it.next();
      usrInput.add(elem+"");
  }
    }
    
    public static void calc(int maxlen,List<String> list,String prefix)
    {
  for (int i = 0; i < list.size(); i++)
  {
      String currentUnit = list.get(i);
      if((prefix+currentUnit).length()==maxlen)
      {
    result.add(prefix+currentUnit);
      }else
      {
    List<String> leftlist = new LinkedList<String>();
    leftlist.addAll(list);
    leftlist.remove(i);
    calc(maxlen,leftlist,prefix+currentUnit);
      }
  }
    }
  
}