Java：字符串到字节数组的转换

Question

I am getting some unexpected results from what I thought was a simple test. After running the following:

byte [] bytes = {(byte)0x40, (byte)0xE2, (byte)0x56, (byte)0xFF, (byte)0xAD, (byte)0xDC};
String s = new String(bytes, Charset.forName("UTF-8"));
byte[] bytes2 = s.getBytes(Charset.forName("UTF-8"));

bytes2 is a 14 element long array nothing like the original (bytes). Is there a way to do this sort of conversion and retain the original decomposition to bytes?

Answer 1

Is there a way to do this sort of conversion and retain the original decomposition to bytes?

Well that doesn't look like valid UTF-8 to me, so I'm not surprised it didn't round-trip.

If you want to convert arbitrary binary data to text in a reversible way, use base64, eg via this public domain encoder/decoder .

Answer 2

This should do:

public class Main
{

    /*
     * This method converts a String to an array of bytes
     */
    public void convertStringToByteArray()
    {

        String stringToConvert = "This String is 76 characters long and will be converted to an array of bytes";

        byte[] theByteArray = stringToConvert.getBytes();

        System.out.println(theByteArray.length);

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args)
    {    
        new Main().convertStringToByteArray();
    }
}

Answer 3

Two things:

1. The byte sequence does not appear to be valid UTF-8

     $ python >>> '\\x40\\xe2\\x56\\xff\\xad\\xdc'.decode('utf8') Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib64/python2.7/encodings/utf_8.py", line 16, in decode return codecs.utf_8_decode(input, errors, True) UnicodeDecodeError: 'utf8' codec can't decode byte 0xe2 in position 1: invalid continuation byte 

2. Even if it were valid UTF-8, decoding and then encoding can result in different bytes due to things like precombined characters and other Unicode features.

If you want to encode arbitrary binary data in a string in a way where you are guaranteed to get the same bytes back when you decode them, your best bet is something like base64.