Multithreading and Multiplexing - An Introduction to Network Programming with Java - page 83

The above example copies the entire contents of the buffer's array and converts
that copy into a String . Another method of the String class that can be very useful
when processing data within a ByteBuffer does the opposite of the above. Method
getBytes converts a specifi ed String into an array of bytes, which may then be writ-
ten to the buffer.
Example
String myStringData = "Just an example";
byte[] byteData = myStringData.getBytes();
buffer.put(byteData);