[jdom-interest] Legal values of line separator

[Elliotte Rusty Harold]

What should we limit the legal values of the line separator to, if
anything?

* \r, \n, and \r\n?

* Any combination of XML allowed white space?

* Anything that might be legal XML text?

We should probably throw an IllegalArgumentException if a bad value is
passed in.

If we do limit users to the three common cases of \r, \n, and \r\n, plus
possibly the empty string, then maybe these should be available as named
constants somewhere, probably using the typesafe enum pattern. Thoughts?

-- 
+-----------------------+------------------------+-------------------+
| Elliotte Rusty Harold | elharo at metalab.unc.edu | Writer/Programmer |
+-----------------------+------------------------+-------------------+ 
|               Java I/O (O'Reilly & Associates, 1999)               |
|            http://metalab.unc.edu/javafaq/books/javaio/            |
|   http://www.amazon.com/exec/obidos/ISBN=1565924851/cafeaulaitA/   |
+----------------------------------+---------------------------------+
|  Read Cafe au Lait for Java News:  http://metalab.unc.edu/javafaq/ | 
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In some cases I want a NoSuch*Exception, when a child or attribute must
be present.
In some cases the child or attribute is optional; then I want null
returned since there is no exceptional situation, and my code should be
simple.

We can have it both ways.
I use a util function getChild that returns a null if the child is
absent.
I prefer the Element.getChild function to behave like this.
The old Element.getChild functions throwing the exceptions may well be
renamed into mustGetChild.
That would do, IMHO.