Chunking Base64 binary data in Java

I’m not an expert but it seems to me that the different methods to encode as Base64 a *binary* stream exposed by Apache Commons don’t chunk for binary inputs or don’t chunk at all, in spite of what their documentation states.
So let me write here a little snippet, which uses guava-libraries, for an already getBytes()-ed string.

private static String b64eChunk(String mstring) {
	String encodedText = Base64.encodeBase64String(mstring.getBytes());

	String myOutput = "";
	for (String substring : Splitter.fixedLength(76).split(encodedText)) {
		myOutput += substring + "\n";

	return myOutput.substring(0, myOutput.length() - 1);

Credits for the guava part: Cowan.


  1. David Phillips

    String building using concatenation is not efficient. You should a StringBuilder instead. But even better, in this example you’re joining strings together, so you can use Guava’s Joiner:

    return Joiner.on(‘\n’).join(Splitter.fixedLength(76).split(encodedText));

    Also, calling getBytes() on String is usually wrong as it uses the platform default character encoding, which means you get different results on different platforms. You usually want getBytes(Charsets.UTF_8)).

    • Carlo

      Thanks. Perhaps deleting this post won’t be a bad idea because after publishing it I’ve learned a few things about Apache Commons.

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