十六进制数与字节数组相互转换方法

public static byte[] hexStringToBytes(String hexString)
{
if (hexString == null || hexString.equals(""))
return null;

hexString = hexString.toUpperCase();
int length = hexString.length() / 2;
char[] hexChars = hexString.toCharArray();
byte[] bytes = new byte[length];
for (int i = 0; i < length; i++)
bytes[i] = (byte) (charToByte(hexChars[i * 2]) << 4 | charToByte(hexChars[(i * 2) + 1]));
return bytes;
}

private byte charToByte(char c)
{
return (byte) "0123456789ABCDEF".indexOf(c);
}

public static String bytesToHexString(byte[] bytes)
{
StringBuilder builder = new StringBuilder("");
if ((bytes == null) || (bytes.length <= 0))
return null;

for (int i = 0; i < bytes.length; ++i)
{
String str = Integer.toHexString(0xFF & bytes[i]);
if (str.length() < 2)
builder.append(0);
builder.append(str);
}
return builder.toString();
}