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));
	 
   }