JAVA -- how to display a file in binary mode

Question

Given a file of any type, how to display its content in binary (hexadecimal) form in the console in JAVA? Suppose I have a txt file, I know how to display its contents. But if the file is a png or zip file, I need to display its content in binary (hexadecimal) form in the console.

Answer 1

Two options would be to either use String formatting:

String.format("%02x", b & 0xff) //Where b is your byte value

Or you could use your byte(s) as an integer(s) and use this method in the Integer class:

Integer.toHexString(int i)

An example:

//Just some image on my hard drive
File file = new File("C:\\Users\\%username%\\Pictures\\Memes\\What_If_I_Told_You.jpg");
StringBuilder builder = new StringBuilder();
try {
    FileInputStream fin = new FileInputStream(file);
    byte[] buffer = new byte[1024];
    int bytesRead = 0;
    while((bytesRead = fin.read(buffer)) > -1)
        for(int i = 0; i < bytesRead; i++)
            builder.append(String.format("%02x", buffer[i] & 0xFF)).append(i != bytesRead - 1 ? " " : "");
} catch (IOException e) {
    e.printStackTrace();
}
System.out.println(builder.toString());

The output of this was: ff d8 ff e0 00 10 4a 46 49 46 00 01 01 01 00 48... etc

-Thomas