Should I recommend sealing classes by default?

Question

In a big project I work for, I am considering recommending other programmers to always seal their classes if they haven\'t considered how their classes should be subclassed. Oft

Answer 1

"...consider[ing] how their classes should be sub classed..." shouldn't matter.

At least a half dozen times over the past few years I've found myself cursing some open source team or another for a sloppy mix of protected and private, making it impossible to simply extend a class without copying the source of the entire parent class. (In most cases, overriding a particular method required access to private members.)

One example was a JSTL tag that almost did what I wanted. I need to override one small thing. Nope, sorry, I had to completely copy the source of the parent.