Protecting Network Data - Beginning J2ME: From Novice to Professional - page 345

The HexCodec class contains a few static methods for converting between byte arrays and
hex encoded strings. The complete class is shown in Listing 18-2.
Listing 18-2. The HexCodec Helper Class
public class HexCodec {
private static final char[] kDigits = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
'a', 'b', 'c', 'd', 'e', 'f'
} ;
public static char[] bytesToHex(byte[] raw) {
int length = raw.length;
char[] hex = new char[length * 2];
for (int i = 0; i < length; i++) {
int value = (raw[i] + 256) % 256;
int highIndex = value >> 4;
int lowIndex = value & 0x0f;
hex[i * 2 + 0] = kDigits[highIndex];
hex[i * 2 + 1] = kDigits[lowIndex];
}
return hex;
}
public static byte[] hexToBytes(char[] hex) {
int length = hex.length / 2;
byte[] raw = new byte[length];
for (int i = 0; i < length; i++) {
int high = Character.digit(hex[i * 2], 16);
int low = Character.digit(hex[i * 2 + 1], 16);
int value = (high << 4) | low;
if (value > 127) value -= 256;
raw[i] = (byte)value;
}
return raw;
}
public static byte[] hexToBytes(String hex) {
return hexToBytes(hex.toCharArray());
}
}
PasswordMIDlet also uses the URLBuilder class, which provides a simple interface for
assembling GET URLs. The URLBuilder class is shown in Listing 18-3.