Why is inheritance bad

If you overload a static method in Java , it is the example of compile time polymorphism. Here, we will focus on runtime polymorphism in java. Inheritance Breaks Encapsulation. Inheritance creates a tight coupling between base and derived classes. And there are cases where tight coupling is preferable, either for performance reasons, or because two or more classes are intended to be used in tandem. The class is not always the proper GranuleOfRelease.

In this Java OOPs concepts tutorial, we will learn four major object oriented principles — abstraction , encapsulation , inheritance , and polymorphism. They are also known as four pillars of the object oriented programming paradigm. Inheritance is a mechanism in which one class acquires the property of another class. With inheritance , we can reuse the fields and methods of the existing class. Hence, inheritance facilitates Reusability and is an important concept of OOPs.

Hierarchical Inheritance. Multilevel Inheritance. Hybrid Inheritance also known as Virtual Inheritance. Advantages of Inheritance The main advantage of the inheritance is that it helps in the reusability of the code. Through inheritance a lot of time and efforts are being saved.

It improves the program structure which can be readable. The program structure is short and concise which is more reliable. The codes are easy to debug. Benefit of using inheritance : A code can be used again and again. Inheritance in Java enhances the properties of the class, which means that property of the parent class will automatically be inherited by the base class. It can define more specialized classes by adding new details. Because inheritance and all subtyping is a specialization of some super-type.

Even when programmers know that they're supposed to do that and very few do. And worse yet, it's not particularly common that you want to actually do that limited specialization since it rarely is useful.

So instead, there's a boatload of programmers misusing inheritance, just to do polymorphism, or to have XY and Z tacking on an extra field is a fragile and often dangerous use of inheritance , or to kinda sorta specialize things yes, Penguin is a Bird , but it's. Fly method doesn't work Sign up to join this community.

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Learn more. Asked 7 years ago. Active 7 months ago. Viewed 43k times. Improve this question. RonaldMunodawafa RonaldMunodawafa 1 1 gold badge 5 5 silver badges 12 12 bronze badges. There is the aspect of taking the parent and child classes as arguments where the parameter is the parent. That is the difference between this question and the possible duplicate.

The contexts of the two questions are different enough to elicit two distinct sets of answers - there is no answer to my question on that question. Inheritance not generally viewed as bad. RonaldMunodawafa Passing a child instance in place of a parent instance is just run of the mill subtyping, which can equally easily be achieved via interfaces.

This is why I think implementation inheritance is bad, while subtyping is good: yegor So, if you know that this or this method should not be overwritten in children classes, then you have to do something accordingly.

Be careful with patterns, I mean: be clear with yourself about what they have been invented, tested, and approved for, and what you could potentially use them for. This is comlpetely different, and very often leads to misuse.

Keep in mind that the Strategy pattern is a form of IoC, first. And as every other pattern, it should be use to solve the problem it had been designed to solve, solely, when identified.

What is Strategy meant for? Which meand that if you do this all the time, your application will do too many things even for simple tasks. Again, using patterns and even less this or that pattern precisely are not a panacea , they do well for very specific problems. Base class to handle this and that. Specializing the toString method in each subclass is very easy, and will cause no specific overhead. Now imagine it via the Strategy pattern.

Call it where you need composition , say where you need not to specialize your classes but to add functionalities to them: this will be a real case where Strategy and more generically, IoC , will be at its best use. I recently found on the web a pretty good Strategy example on a search engine sort of class.

Whet it came to sorting, the developper felt that it had no real binding to searching, actually and to me he was right. Clearly at least to me , this is when IoC patterns should be used. Basically, it is sort of a substitute for sub-classing, but it should be used in some specific occasions only as always with patterns. Sounds like the problem is a lack of Interfaces. DarkJediPowers should be an interface that anyone can implement.

Interfaces when all implementations are best represented using multiple inheritance of course. Then again in my experience it is rare that a DarkHippo is going to crush villagers in the same way a DarkJedi will. The classic diamond problem is solved by the compiler mentioning the ambiguity of your code. I have bent over backwards trying to find a work around to not having multiple inheritance in C or same thing with Java, AS3. The best I can do is create an interface of the second class I want to derive from and, eeeeeeeeewwwwww, copy and paste the implementations of its methods.

Such a shame. I blame Java for this. Correct me if im wrong but they are the bastards that started the whole interface thing. Pink at the top of the page template is eye bleeding ff The bottom color of the gradient bd goes nice with the textured grey.

I disagree. You are free to respect this IsXxx contract by either inheritance or aggregation. Even you are no more concerned by method name collision. Actually i think the mostly used of inherintance is to simplify a composition. Skip to content. Bernard, you are fighting the good fight. This becomes more convenient with ActionScript or classes written in the MS Atlas framework, since this works: myAlgorithm.

For example, you could make a PropertyChangeStrategy class that holds a number of strategies and applies them to its containing object each frame: ball. But the example makes sense. In my understanding, OOAD is about mapping concepts into interacting objects, not hierarchies. Firstly, good example; my argument is that Customer has-a CorporateRelationship is better.

Secondly, the Strategy Pattern is just fine for invariant relationships. Mmm I agree that Inheritance is often used in a bad way. Ahh now I understand. I think I misunderstood what you mean exactly by Inheritance. Thanks again. Yeah, I do tend to use the term Strategy Pattern when I really mean composition. It points out the problems with inheritance very well. Perhaps this kind of a view will help someone to look at their classes in a different way.

Hi there, Heads on! Hey Bernie, I think you are right in many regards and you are defiantly on the right track, however I feel your example is slightly off. If the former, then quite so: good Jedi would no doubt help townspeople.

Just a thought. An interesting point — I was thinking about class-based languages when I wrote the piece. Thanks for the awesome article. Really thorough. Well done! What am I missing? The software world would be a better place is inheritance never was introduced. Kevin McLaughlin. Pingback: Inheritance is evil blog-of "Alex Shabanov". Bernie, nice article. You are a cargo cultist of the worst kind.

However, your article will cause me to reflect on my uses of inheritance. Inheritance is God when it is used correctly is wonderful, otherwise is only a mistake.

Bernie : o. Oh, another thing, also take a look at the DCI architecture…. In your example clearly Darkness belongs in another class.

Chase cat This could be written as a method, void Dog. The goal is always single purpose small classes. Consider using a Tweener for your animation. Pingback: Bonnes pratique de codage en C. Pingback: Bonnes pratique de codage en C « Hakanai.

Bernie :o. Yes, and yes.. I see your point. However: a if the designer of the base class did not intend the methods to be overridden, then overriding them may create random odd bugs, but b if the designer did intend the methods to be overridden, then they could just as easily define a strategy interface that you can use to pass in an object representing your intended customisations. Your Ball example actually works equally well with this!

The main reason of inheritance is to reduce duplicated code, the child class can share the implementation from parent class. This is a extra benefit that, if the class hierarchy defined well, can help to make system easy to understand. Above code is a web service that send request to an endpoint and retrieve response.

Because there are multiple services, we extract the common code into ServiceBase to reduce duplication. The behavior of jumping back and forth from parent and child classes, we called it Yo-Yo problem.

Inheritance creates dependency between child and parent, when a class inherit another class, we include all methods and attributes from parent class and expose to the child class, therefore we break the encapsulation, the child object can access all the methods in parent object and overwrite them. That creates a tightly coupled relation between child and parent class, also against the idea of object oriented, which is hide the complexity in the object and interact by interface.

Also when we read the child class, we needs to understand the implementation details of the parent class because it expose the complexity to child class, verses hiding it in the object. Inheritance, by the rule of substitution, needs to inherit all the methods and properties from parent class, even if it is not used or not needed in the child class, that creates more complexity than the child class needs to.

Because we can only inheritance from one class, if we extract all the code into ServiceBase , it is hard to reuse just part of the code without includes all the methods in ServiceBase.