src/main/java/net/glowstone/util/Convert.java

package net.glowstone.util;

public class Convert {
    public static byte[] fromHex(String hex) {
        int len = hex.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(hex.charAt(i), 16) << 4) + Character.digit(hex.charAt(i + 1), 16));
        }
        return data;
    }

    public static String fromBytes(byte[] bytes) {
        StringBuilder sb = new StringBuilder(40);
        for (byte b : bytes) {
            sb.append(String.format("%02X ", b));
        }
        return sb.toString();
    }
}