code: public static String bytesToHexString(byte[] b) {
  		StringBuffer sb = new StringBuffer();
  		String hex;
  		for (int i = 0; i < b.length; i++) {
  			hex = Integer.toHexString(b[i] & 0xff);
  			if (hex.length() == 1) {
  				hex = '0' + hex;
  			}
  			sb.append(hex.toUpperCase());
  		}
  		return sb.toString();
  	}
docs: 将一个字节数组转化成十六进制字符串并返回
  
  @param b
  字节数组
  @return 返回一个由十六进制字符组成的字符串