The things that mostly stick out for me are “code smells”. Mostly I’m sensitive to things that go against “good practice”. Things like: Methods that do things other than what you’d think from the name (eg: FileExists() that silently deletes zero byte files) A few extremely long methods (sign of an object wrapper around a … Read more
You have missed the point. The valid, important bit of that article is: Don’t ask for the information you need to do the work; ask the object that has the information to do the work for you. Java-style getter and setter proliferation are symptoms of ignoring this advice.
You can use a metaclass: class SampleMeta(type): def __str__(cls): return ‘ I am a Sample class.’ Python 3: class Sample(metaclass=SampleMeta): pass Python 2: class Sample(object): __metaclass__ = SampleMeta Output: I am a Sample class. A metaclass is the class of class. Its relationship to a class is analogous to that of a class to an … Read more
Why is this interface used? Because it supports the basic operations that would allow a client programmer to iterate over any kind of collection (note: not necessarily a Collection in the Object sense). Why are the methods… not directly coded to the data structure implementation itself? They are, they’re just marked Private so you can’t … Read more
Types determine the granularity of composition, i.e. of extensibility. For example, an interface, e.g. Comparable, that combines (thus conflates) equality and relational operators. Thus it is impossible to compose on just one of the equality or relational interface. In general, the substitution principle of inheritance is undecidable. Russell’s paradox implies that any set that is … Read more
“Fields”, “class variables”, and “attributes” are more-or-less the same – a low-level storage slot attached to an object. Each language’s documentation might use a different term consistently, but most actual programmers use them interchangeably. (However, this also means some of the terms can be ambiguous, like “class variable” – which can be interpreted as “a … Read more
I’m not sure about Java in particular, but it should be valid. In terms of OOP, if it makes sense, then run with it. To use some old examples, you might have a Vehicle abstract class and then LandVehicle and FlyingVehicle abstract classes. As long as your example makes sense as an abstract class, then … Read more
I can see one advantage for the object adapter, depending on your programming language: if the latter does not support multiple inheritance (such as Java, for instance), and you want to adapt several adaptees in one shot, you’ll be obliged to use an object adapter. Another point for object adapter is that you can have … Read more
Use class.equals(): if (nextMonster.getClass().equals(monster.getClass())) or, because each class is like a singleton – there’s only one instance of each Class per class loader, and most JVMs only have the one class loader – you can even use an identity comparison: if (nextMonster.getClass() == monster.getClass())