How to convert byte array to hex format in Java

Question

I know that you can use printf and also use StringBuilder.append(String.format("%x", byte)) to convert values to HEX values and display them on the console. But I want to be able to actually format the byte array so that each byte is displayed as HEX instead of decimal.

Here is a section of my code that I have already that does the first two ways that I stated:

if(bytes > 0)
    {
        byteArray = new byte[bytes]; // Set up array to receive these values.

        for(int i=0; i<bytes; i++)
        {
            byteString = hexSubString(hexString, offSet, CHARSPERBYTE, false); // Isolate digits for a single byte.
            Log.d("HEXSTRING", byteString);

            if(byteString.length() > 0)
            {
                byteArray[i] = (byte)Integer.parseInt(byteString, 16); // Parse value into binary data array.
            }
            else
            {
                System.out.println("String is empty!");
            }

            offSet += CHARSPERBYTE; // Set up for next word hex.    
        }

        StringBuilder sb = new StringBuilder();
        for(byte b : byteArray)
        {
            sb.append(String.format("%x", b));
        }

        byte subSystem = byteArray[0];
        byte highLevel = byteArray[1];
        byte lowLevel = byteArray[2];

        System.out.println("Byte array size: " + byteArray.length);
        System.out.printf("Byte 1: " + "%x", subSystem);
        System.out.printf("Byte 2: " + "%x", highLevel);
        System.out.println("Byte 3: " + lowLevel);
        System.out.println("Byte array value: " + Arrays.toString(byteArray));
        System.out.println("Byte array values as HEX: " + sb.toString());
    }
    else
    {
        byteArray = new byte[0]; // No hex data.

        //throw new HexException();
    }

    return byteArray;

The string that was split up into the byte array was:

"1E2021345A2B"

But displays it as decimal on the console as:

"303233529043"

Could anyone please help me on how to get the actual values to be in hex and be displayed in that way naturally. Thank you in advance.

Answer 1

String.format actually makes use of the java.util.Formatter class. Instead of using the String.format convenience method, use a Formatter directly:

Formatter formatter = new Formatter();
for (byte b : bytes) {
    formatter.format("%02x", b);
}
String hex = formatter.toString();

As of Java 17, HexFormat can do this in one line:

String hex = HexFormat.of().formatHex(bytes);