Hex library

Hex library converts bytes to the hex representation and vice versa.

HexHelper class contains methods to convert the byte array to the hex string, to convert the hex string to the byte array and to check, whether the string is a hex representation of bytes or not.

An example, how to convert the byte array to the hex string:

String str1 = HexHelper.toHex(new byte[]{1, 5, (byte) 140, (byte) 250, -14}); // str1 = "01058cfaf2"
String str2 = HexHelper.toHex(new byte[]{17, 28, (byte) 179, -14}); // str2 = "111cb3f2"
String str3 = HexHelper.toHex(new byte[]{(byte) 255, (byte) 250, (byte) 180, 17, 94}); // str3 = "fffab4115e"

An example, how to convert the hex string to the byte array:

byte[] bytes1 = HexHelper.toBytes("AC120F"); // bytes1 = new byte[]{(byte) 172, 18, 15}
byte[] bytes2 = HexHelper.toBytes("AACD2F"); // bytes2 = new byte[]{(byte) 170, (byte) 205, 47}
byte[] bytes3 = HexHelper.toBytes("aacd2f"); // bytes3 = new byte[]{(byte) 170, (byte) 205, 47}

HexHelper class contains all data in memory. For the large data (for example, big files) this is not efficient. In this case HexInputStream and HexOutputStream classes can be used. HexInputStream reads the stream of the hex characters and translates them to the bytes. HexOutputStream translates the bytes to the hex characters and writes them to the stream.

An example, how to write the hex characters to the file:

try (FileInputStream inputStream = new FileInputStream("input file");
     HexOutputStream outputStream = new HexOutputStream(new FileOutputStream("hex output file"))) {
    int b;
    while (true) {
        b = inputStream.read();
        if (b < 0) {
            break;
        }
        outputStream.write(b);
    }
}

Each byte is represented with two hex characters. The hex representation of bytes increases the original size twice.