Question

I have come across this line of legacy code, which I am trying to figure out:

String newString = new String(oldString.getBytes("UTF-8"), "UTF-8"));

As far as I can understand, it is encoding & decoding using the same charSet.

How is this different from the following?

String newString = oldString;

Is there any scenario in which the two lines will have different outputs?

p.s.: Just to clarify, yes I am aware of the excellent article on encoding by Joel Spolsky !

Answer 1

This could be complicated way of doing

String newString = new String(oldString);

This shortens the String is the underlying char[] used is much longer.

However more specifically it will be checking that every character can be UTF-8 encoded.

There are some “characters” you can have in a String which cannot be encoded and these would be turned into ?

Any character between \uD800 and \uDFFF cannot be encoded and will be turned into ‘?’

String oldString = "\uD800";
String newString = new String(oldString.getBytes("UTF-8"), "UTF-8");
System.out.println(newString.equals(oldString));

prints

false