How to convert byte array to string and vice versa?

Solution 1:

Your byte array must have some encoding. The encoding cannot be ASCII if you've got negative values. Once you figure that out, you can convert a set of bytes to a String using:

byte[] bytes = {...}
String str = new String(bytes, StandardCharsets.UTF_8); // for UTF-8 encoding

There are a bunch of encodings you can use, look at the supported encodings in the Oracle javadocs.

Solution 2:

The "proper conversion" between byte[] and String is to explicitly state the encoding you want to use. If you start with a byte[] and it does not in fact contain text data, there is no "proper conversion". Strings are for text, byte[] is for binary data, and the only really sensible thing to do is to avoid converting between them unless you absolutely have to.

If you really must use a String to hold binary data then the safest way is to use Base64 encoding.