Should i use static methods

In functional programming, all functions must have explicit inputs and outputs I call this practice method signature honestry. This practice leads to code that is extremely easy to understand and maintain. It looks clean at first glance, but in reality, this class works with hidden inputs and thus suffers maintainability-wise.

For this code to work properly, you need to always remember which method depends on what in order to always call them in the right order:. If you mess up with that order, the code will fail at runtime.

For example, if you put the second method call above the first one:. When you learn about functional programming, you start to understand that static methods are evil only if they work with shared state. For example, when they allow you to read or modify the state of a global variable. Without state changes, these two points cease to be an issue.

Min a, b , right? Because a static variable belongs to the class itself, there is only one of it, not one for each object. If you change the value of this variable, it is changed in the class. Individual Dog objects can use static variables just like any other because every object knows what class it belongs to , but individual dogs don't have a "count.

That doesn't make sense. Likewise, a static method no example shown belongs to the class itself, not to individual objects of that class.

Active 9 months ago. Viewed 1. I'm rather confused! Lii KP65 KP65 Add a comment. Active Oldest Votes. So in a class Car you might have a method: double convertMpgToKpl double mpg But this method which sets the efficiency of one particular Car : void setMileage double mpg A few good examples here.

I would add, however, that "static" is often valuable when you know something is not going to change across instances. If this is the case, I would really consider the "Single Responsability Principle", which implies a class should have one responsability and thus only one reason to change.

I feel one should consider moving the "ConvertMpgToKpl double mpg " function, and similar methods, to their own class. The purpose of a car object is to allow instantiation of cars, not provide a comparison between them. Those should be external to the class.

It has the advantage that which car you return in a tie isn't arbitrary. It's obvious by the title of the method what is returned in a tie. I would also be careful about creating a static method that is using some external resource filesystem, database, etc this type of static can make it horrendous to test the consuming methods.

I personally try to keep statics in the realm of "utility. In fact, it should be implemented as a Comparator. B1KMusic Of course.

What I mean by "which car is returned in a tie" is "true maps to the called on car, and false maps to the passed car". It's without ambiguity. Show 12 more comments. Define static methods in the following scenarios only: If you are writing utility classes and they are not supposed to be changed.

If the method is not using any instance variable. If any operation is not dependent on instance creation. If there is some code that can easily be shared by all the instance methods, extract that code into a static method. If you are sure that the definition of the method will never be changed or overridden. As static methods can not be overridden. Simon Forsberg Mohd Mohd 5, 1 1 gold badge 12 12 silver badges 2 2 bronze badges. Aren't there always unknown factors you can't take in account at the moment you write your static method?

Prefer objects first. Mohd this answer is exactly what I am looking for. I faced a lot of problems using static methods in multithreading. Can you please elaborate points 2, 3 more with example thumbs up for you — Prakash Pandey. I think a "static class" should be invented if you are going to use static variables and methods. Show 1 more comment. There are some valid reasons to use static methods: Performance : if you want some code to be run, and don't want to instantiate an extra object to do so, shove it into a static method.

A lot of good reasons listed here on when static can be useful. One more I can think of is that writing unit tests for such methods is just plain simple — nilesh. Your explanation is very clear and the reasons provided are very logical and make a lot of sense.

That said a static method becomes a full named function stackoverflow. I agree with Performance and Practicality, but not Purity. The static method can modify static members of the class which may be private.

This can be useful. In fact, a static method can be just as pure or impure as a non-static method in terms of side effects. The basic issue with static methods is they are procedural code The basic issue with static methods is they are procedural code. Alfred Alfred I don't understand the part about not being able to unit-test procedural code.

Don't you just set up test cases that map correct input to correct output using the static method together with the class as your "unit"?

You could do that to test those functions. Alfred: Please have a look at PowerMock which has the ability to mock static methods.

Using PowerMock there are few scenarios, if any, where you find method dependencies which cannot be mocked. Share to Twitter Share to Facebook. Labels: core java , Java Programming Tutorials. July 15, at AM Anonymous said July 18, at PM Anonymous said July 29, at AM Satyam said December 6, at PM Satyam said Great article December 6, at PM Anonymous said January 20, at PM Anonymous said April 11, at AM Dhanashree said August 2, at AM.

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