Good advice.

Constructors are for construction, only.  Logic belongs in methods.  The
object isn't constructed until the constructor finishes, so generally one
should not do anything non-constructive (such as calling an overridable method
or registering an event listener) in a constructor.

For one thing, it is a thread safety issue.  Along with the general
practice that you should not allow the "this" pointer to escape during
construction.  The "this" pointer is only fully valid once the
constructor has completed normally.  If you need to register listeners
as part of the instantiation process, consider using a static factory
method which instantiates a private constructor, and then attaches that
instance to the appropriate places.

If you want an indepth explanation of why it is dangerous, along with a
lot of other good-to-have understanding of multi-threaded programming, I
suggest getting the book /Java Concurrency In Practice/. You can read my
short review of it at
<http://virtualinfinity.net/wordpress/technical-book-recommendations/>
.

Good luck,
Daniel.