Java generic convert byte array to string (Non hex, decimal)

Question

What is the best way to convert a byte array to a string with a radix of choice? There is a ton of examples here on S.O. and elsewhere to convert to a hex string. What I am mainly interested in here is converting to something other than a hex or decimal string; also a more generic way.

This is what I currently do:

byte[] input;
String MyStr = new BigInteger(input).toString(radix);

This works, but since Java has a concept of radix, as used in the Integer. This seems to be the explicit purpose as defined in Character. Shouldn't there be a better way of doing this rather than to first convert the byte array to a BigInteger? It feels like my Java knowledge misses some essential standard class?

EDIT: I would like to use this for a compressed way of representing (and printing) raw binary data of different types. This is the actual radix I currently use:

String MyStr = new BigInteger(data).toString(Character.MAX_RADIX);

The MAX_RADIX (36) uses a combination of lower case letters and numbers. This gives a decent compression, but would be even better if the radix could include UPPER letters, which is why I thought I may be missing something.

Can you give examples of the bytes and what you expect as the result? — Bohemian
– Bohemian ♦, Commented Feb 24, 2015 at 22:11
It looks like a very object oriented way to me, you get the value representation which is then translated to string. Are you worried about performance? The code at least is self explanatory. — Zielu
– Zielu, Commented Feb 24, 2015 at 22:14
I'm assuming your input is a byte[], not a Byte[], since there's no BigInteger constructor that takes a Byte[]. — ericbn
– ericbn, Commented Feb 24, 2015 at 22:43

ericbn · Accepted Answer · 2015-02-25 12:26:55Z

3

It seems like you're looking for Base64 encoding. This uses 64 different characters to encode a value: upper case and lower case letters (that's 52 characters already), digits (10 more, including the '0'), and the '+' and '/' symbols (or '-' and '_' in the url-safe variation).

If you're using Java 8, there's the Base64 class:

String str = Base64.Encoder.encodeToString(data);

Otherwise, Apache Commons has a Base64 class too:

String str = Base64.encodeBase64String(data);

edited Feb 25, 2015 at 12:26

answered Feb 24, 2015 at 22:38

ericbn

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1 Comment

Andy Over a year ago

Thanks! This is useful, and great its now part of Java8. I should have thought of that. I still sometimes need the radix to be 2 and 16 for debugging, but for the most part, Base64 should be ok.

Marcelo Tataje · Accepted Answer · 2015-02-24 22:13:25Z

0

That's a good one, actually, I'm not sure neither if there's a class to achieve that. But another way to do what you want without using BigInteger is to iterate over the array and get the output, something like:

for(byte b : input){
    System.out.print(Integer.toString(b & 0xFF, radix));
}

Not sure about an specific class doing a conversion, but this is another approach I know, maybe could be useful to you or to somebody else.

Happy coding.

Regards.

answered Feb 24, 2015 at 22:13

Marcelo Tataje

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