Convert char hex array to byte array java

Question

How can I convert a char array of hex to byte array in Java? I don't want to convert char array to string for security reasons.

Is there any inbuilt library available for this conversion in Java 8?

What do you mean? How does security is compromised if converted to `String`? — Mushif Ali Nawaz, Sep 24 '19 at 17:34
I can clear the char array by Arrays.fill but if converted to string it will be dependent on gc in java — Dark Matter, Sep 24 '19 at 17:36
You might want to [check this answer](https://stackoverflow.com/a/9670279/5413565) — Mushif Ali Nawaz, Sep 24 '19 at 17:42
@Mushif Ali Nawaz See [Why is char array preferred over String for passwords?](https://stackoverflow.com/questions/8881291/why-is-char-preferred-over-string-for-passwords) — Nexevis, Sep 24 '19 at 17:42
Possible duplicate of [Converting char\[\] to byte\[\]](https://stackoverflow.com/questions/5513144/converting-char-to-byte) — Mushif Ali Nawaz, Sep 24 '19 at 17:43
Do you mean that each char value is a hexadecimal digit? Meaning, ASCII `0`–`9` or `a`–`f` or `A`–`F`? — VGR, Sep 24 '19 at 17:57
@VGR yes the char array is randomly generated hexadecimal array I have to convert it to byte array, I tried Bytebuffer bytebuffer = StandardCharsets.UTF_8.encode(Charbuffer.wrap(chrarr)) but this is just doing the utf8 conversion not hex conversion — Dark Matter, Sep 24 '19 at 18:07

score 0 · Accepted Answer · answered Sep 24 '19 at 18:08

There is no single Java SE method for it, but with Character.digit it’s fairly straightforward:

byte[] parse(char[] hex) {
    int len = hex.length;
    if (len % 2 != 0) {
        throw new IllegalArgumentException(
            "Even number of digits required");
    }

    byte[] bytes = new byte[len / 2];
    for (int i = 0; i < len; i += 2) {
        int high = Character.digit(hex[i], 16);
        int low = Character.digit(hex[i + 1], 16);
        bytes[i / 2] = (byte) (high << 4 | low);
    }

    return bytes;
}

Convert char hex array to byte array java

1 Answers1