translate.java

public static void main(String[] args) throws Exception {
    File file = new File("test.txt");
    FileInputStream is = new FileInputStream(file);
    
    FileOutputStream os = new FileOutputStream("test.7z");
    int k;
    char[] ka = new char[2];
    int i=0;
    while((k = is.read()) != -1)
    {
        ka[i++] = (char)k;
        if(i==2)
        {
            int s = Integer.parseInt(new String(ka), 16);
            os.write(s);
            i = 0;
        }
    }
    //ignore exception handle
    os.close();
    is.close();
}