Monthly Archives: February 2013

Trending up: Windows7, Agile Methodologies, Scrum, Python. Everything else? Down!


Linked-in are now listing ala-carte qualifications which one can endorse one’s acquaintances on, or be endorsed by them. No surprise, 20 people say I’m good at “hardware”, which is my highest endorsement. What I want to draw your attention to here is that if you hover your pointer over each of the possible qualifications, Linked-in will show you a working definition and the year-to-year trend on people who say they do-have-know-practice-are-qualified-in the specific item.

Not so surprising, people saying they know ‘hardware’ are down year on year… also C, C++, software engineering, Perforce, customer support, regression test, unit test, and so forth. VMware is 0% – neither up nor down over last year.

Agile Methodologies are up, Windows 7 is way-up, Python is up, Scrum is up. The other 44 categories, on my list, not including VMware at 0 and Windows 8 which doesn’t have a year on year trend, are down.

So, among people who list qualifications similar to mine, the majority and growth area are Python users, on Windows 7, employing Scrum and Agile project management methods.

Your choice whether that’s:

a) what everyone wants;

b) what people looking for work think they need;

c) some cross section of professionals on Linked-in.

I think its worth noting in passing, but not worth a lot of study. But it is a curiosity.

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An example that pleased me: The difference between an abstract class and an interface, in Java:


Here’s the punch line:

In Java, Prussia can extend (“be a”) one of the super-classes, Holy, Roman or  Empire, but only one. Prussia can implement the other two as interfaces, but only with methods and fields uniquely its own. If Prussia is to be Holy, be Roman and be an Empire, the strictly hierarchical relationship of those three super-classes has to be worked out separately and in detail, in advance. I can only imagine Herr von Bismark would approve.

 

And the whole magilla:
1) What is the difference between an interface and an abstract class?

An abstract class defines data (fields) and member functions but may not, itself, be instantiated. Usually, some of the methods of an abstract class are abstract and expected to be supplied by a sub-class, but some of the methods are defined.  Unless they are final, they can be overridden, and they can always be overloaded. Private parts of an abstract super class, for example, data, are not available to a subclass, so access methods (public or protected) must be used by the subclass. An abstract superclass is “extended” by a subclass. A given subclass may only extend one super-class, but a super-class may extend another super-class, in a hierarchy. (This avoids the complexities/difficulties of multiple inheritance in C++)

An interface is a proper subset of an abstract class, but has a different scope and use. An interface has ONLY abstract member functions and static, final, fields, aka constants. Any subclass has to provide all the variable fields and code which implements an interface. The implementing class cannot override the interface’s member signatures – the signatures are what the interface *is*. It is possible to overload an interface’s signatures, adding or subtracting variables, changing return or variable types, but the overloads do not satisfy the requirements of the interface. The implementing class(s) must contain actual member functions to satisfy all of the signatures in the interface, because there is no default, no code in the interface.  As used above, a given class ‘implements’ an interface, it does not ‘extend’ it. These limitations to an interface allow a given class to implement more than one, which retains most of the utility of multiple inheritance without, as it were, opening Plethora’s bag. (grin)

For example: In Java, Prussia can extend (“be a”) one of the super-classes, Holy, Roman or  Empire, but only one. Prussia can implement the other two as interfaces with methods and fields uniquely its own. If Prussia is to be Holy, be Roman and be an Empire, the strictly hierarchical relationship of those three super-classes has to be worked out separately and in detail, in advance. I can only imagine Herr von Bismark would approve.