给定一字符数组,求数组中字符组成的所有排列

public static void main(String[] args)   {    char[] origin = { 'a', 'b', 'c', 'd', 'e', 'f' };    int length = origin.length;    int[] tmp = new int[length];    char[] res = new char[length];    boolean[] check = new boolean[length];    int index = 0, level = 0;    while (true)    {     if (index >= 0 && index < length && level >= 0 && level < length)     {      if (!check[index])      {       tmp[level] = index;       res[level] = origin[index];       check[index] = true;       level++;       index = 0;      }      else      {       index++;      }     }     else if (level >= length)     {      System.out.println(new String(res));      level = length - 1;      index = tmp[level];      check[index] = false;      index++;     }     else if (index >= length)     {      level--;      if (level < 0)       break;      index = tmp[level];      check[index] = false;      index++;     }     else     {      break;     }    }   }