Convert a string array to a byte array (java)

Question

I saved this byte array as a string in my database :

public static final byte[] NEW_KEY_2KTDES = {
    (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00,
    (byte)0x00, (byte)0x00, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff, (byte)0xff,
    (byte)0xff
};

Now I want to get this string from my db and convert it to a byte array (like above). I tried to do it :

String[] str_pass = obj.getString("password").split(" "); 
byte[] NEW_KEY = convertToBytes(str_pass);

But that convertToBytes function is the problem :

private static byte[] convertToBytes(String[] strings) {
    byte[] data = new byte[strings.length];
    for (int i = 0; i < strings.length; i++) {
        String string = strings[i];
        data[i] = string.getBytes(Charset.defaultCharset()); // you can chose charset
    }
    return data;
}

Is there a better way ?

Mo Meshkani · Accepted Answer · 2018-02-24 11:21:14Z

3

an array of bytes is just one String so you should use a two dimensional byte array

private static byte[][] convertToBytes(String[] strings) {
    byte[][] data = new byte[strings.length][];
    for (int i = 0; i < strings.length; i++) {
        String string = strings[i];
        data[i] = string.getBytes(Charset.defaultCharset()); // you can chose charset
    }
    return data;
}

answered Feb 24, 2018 at 11:21

Mo Meshkani

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4 Comments

Top Stars Over a year ago

But I want a byte[]

Mo Meshkani Over a year ago

it will return byte array of every element in the string array

Top Stars Over a year ago

My target is getting a byte[] array of whole string. Each element of string is a byte.

Mo Meshkani Over a year ago

Convert whole array into one string first using join and then use string.getBytes()

goodev · Accepted Answer · 2018-02-24 11:19:08Z

Change your bytes array to Hex String and save to database, and convert Hex String to bytes array back:

public class HexUtils {
    private static final char[] HEX_ARRAY = {'0', '1', '2', '3', '4', '5', '6',
            '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    public static String encodeWithHex(@NonNull byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        for (int i = 0, j = 0; i < bytes.length; i++, j += 2) {
            int v = bytes[i] & 0xFF;
            hexChars[j] = HEX_ARRAY[v >>> 4];
            hexChars[j + 1] = HEX_ARRAY[v & 0x0F];
        }
        return new String(hexChars);
    }

    public static byte[] fromHexString(@NonNull String hexStr) {
        hexStr = hexStr.replace(" ", ""); // support spaces
        if (hexStr.length() % 2 != 0) {
            throw new IllegalArgumentException("Invalid HEX string " + hexStr);
        }

        byte[] result = new byte[hexStr.length() / 2];
        for (int i = 0; i < result.length; i++) {
            int high = fromHexChar(hexStr, i * 2) << 4;
            int low = fromHexChar(hexStr, i * 2 + 1);
            result[i] = (byte) ((high | low) & 0xFF);
        }
        return result;
    }

    private static int fromHexChar(String hexStr, int index) {
        char ch = hexStr.charAt(index);
        if (ch >= '0' && ch <= '9') {
            return ch - '0';
        } else if (ch >= 'a' && ch <= 'f') {
            return 10 + (ch - 'a');
        } else if (ch >= 'A' && ch <= 'F') {
            return 10 + (ch - 'A');
        } else {
            throw new IllegalArgumentException("Invalid HEX string: " + hexStr);
        }
    }

}

Nice job, I used encodeWithHex to save to my db and used fromHexString to read from db.

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