Why Java extends only one class?
From SCJP 6 study guide:
"Some languages (like C++) allow a class to extend more than one other class.
This capability is known as "multiple inheritance." The reason that Java's
creators chose not to allow multiple inheritance is that it can become quite
messy. In a nutshell, the problem is that if a class extended two other classes,
and both superclasses had, say, a doStuff() method, which version of doStuff()
would the subclass inherit? This issue can lead to a scenario known as the
"Deadly Diamond of Death," because of the shape of the class diagram that
can be created in a multiple inheritance design. The diamond is formed when
classes B and C both extend A, and both B and C inherit a method from A. If
class D extends both B and C, and both B and C have overridden the method
in A, class D has, in theory, inherited two different implementations of the
same method. Drawn as a class diagram, the shape of the four classes looks
like a diamond."
