// Decode base64.
ByteString a = ByteString.decodeBase64("bWFwbGUgc3lydXA=");
// Encode base64.
String b = a.base64();
// Decode hex.
ByteString c = ByteString.decodeHex("776166666c6573");
// Encode hex.
String d = c.hex();
// Read from an input stream.
ByteString e = ByteString.read(new FileInputStream("foo.txt"), 50);
// Write to an output stream.
a.write(new FileOutputStream("bar.bin"));
// Encode UTF-8.
ByteString f = ByteString.encodeUtf8("petit déjeuner");
// Decode UTF-8.
String g = a.utf8();
// Use a byte string as a Map key (uses equals() and hashCode().)
Map<ByteString, String> map = new LinkedHashMap<>();
map.put(a, "decoded base64");
map.put(c, "decoded hex");
map.put(e, "read an input stream");
// Copy the bytes into an array.
byte[] h = a.toByteArray();
The entire jar is less than 100 KiB so you shouldn't hesitate to include it wherever you need it.
Get Okio on GitHub.