Trees versus Forests

There are two common views of class hierarchies:

• All classes are part of a single large class hierarchy. Thus, there is one class that is the original ancestor of all other classes.
  Smalltalk, Java and Delphi Pascal do this.

• Classes are only placed in hierarchies if they have a relationship - results in a forest of many small hierarchies, but no single ancestor.
  C++, Objective-C, and Apple Object Pascal do this.