Need to copy the code also to 3.0 version

It always surprises me how things change when one really tries to implemente them. The whole approach with non-monotinic evolution was uncompilable. We need a common super type for all the visitors\!

Clean definition of the version using interfaces

Expose as less as possible - making constructor of Expression package private

In order to provide better navigation in the Visitor examples, I will prefix them with a number

Last clashing code section for now. Time to sleep

Duplicated code section

Closing up examples of visitor based on abstract class

There was some mischmash between abstractclass and unknownvisit, hopefully fixing it

default traversal described

Fix broken compilation

visitUnknown method introduced

Visitor pattern with abstract class is relatively good

Example with non-extensible visitor

Changed to match the example in the book

Full coverage is not enough

Adding example, however only a sketch, of possible runtime check between alternative versions

Merge: Geertjan's changs up to 2000

up to line 2000

Checking that all examples pair the opening and closing brackets

Adding example with factory method for unsynchronized StringBuffer

Yet another use of Arithmetica

Another use for Arithmetica

Using Arithmetica for yet another example

Alternative behaviour with constructor described on Arithmetica example

Improved to look better in the book code sample

Shortening too long line

Design part is cleared from the non-colorized code snippets

Special project for inidividual samples, used to show code that can be called only from test

Example showing that factory methods have greater flexibility when typing with generics