随机数字组成密码

private static Random random = new Random();

    public static String getRandomNumber(String[] range,int rangeLength,int length){

    	StringBuffer sb = new StringBuffer();

	      for(int i=0;i<length;i++){

	           sb.append(String.valueOf(range[random.nextInt(rangeLength)]));

	       }

	        return sb.toString();

	    }

   public static void main(String[] args) {

      String[] range = {"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","A","B","C"};

	      System.out.println(getRandomNumber(range, 20, 6));

   }