Java : Byte array prints unknown values for same string

Question

I have the following String which is stored in a text file and also as a variable in Java : ‘destructive’

My code below

public class SimpleTest {

    public static void main(String[] args) {
        try {
            File file = new File("TestFIle.txt");
            byte[] file_encoded = FileUtils.readFileToString(file, "UTF-8").getBytes("UTF-8");
            System.out.println(Arrays.toString(file_encoded));

            String toEncrypt = "‘destructive’";
            byte[] encoded = toEncrypt.getBytes(Charset.forName("UTF-8"));
            System.out.println(Arrays.toString(encoded));
        } catch (IOException ex) {
            Logger.getLogger(SimpleTest.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

As you can see

String toEncrypt = "‘destructive’";

The contents in TestFIle.txt is also : ‘destructive’

When i run the code i get:

[-17, -69, -65, -30, -128, -104, 100, 101, 115, 116, 114, 117, 99, 116, 105, 118, 101, -30, -128, -103]
[-30, -128, -104, 100, 101, 115, 116, 114, 117, 99, 116, 105, 118, 101, -30, -128, -103]

What is the additional [-17, -69, -65] at the starting of byte array while reading the same text from a file and why do i get that?

rmunge · Accepted Answer · 2020-10-19 12:00:49Z

1

Your file seems to contain text encoded in UTF-8 with a leading byte order mark (BOM). The BOM for UTF-8 is EF BB BF. In two's complement representation this is -17 -69 -65.

answered Oct 19, 2020 at 12:00

rmunge

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Comments

gillesB · Accepted Answer · 2020-10-19 11:54:37Z

0

The leading [-17, -69, -65] is the byte order mark of UTF-8. In hexadecimal the BOM is [0xEF, 0xBB, 0xBF] which is actually [239, 187, 191]. But because Java's byte is signed, the numbers are interpreted (and printed) as negative numbers.

In general, the BOM is optional and it seems to be common in the Microsoft ecosystem: https://superuser.com/questions/1553666/utf-8-vs-utf-8-with-bom

answered Oct 19, 2020 at 11:54

gillesB

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