First, encapsulate any such potentially hazardous code into its own class or method. Remember that it is horrible if you tried to edit third-party classes on your own. A long method is a good example of this - just looking at the code and my nose twitches if I see more than a dozen lines of java. In that case, it would be better to move this logic from User class to UserContactDetails class and create getWelcomeMessage($userName). Not using @Override on a method which overrides a parent class method or implements a method interface. Global Variable Class. Learn from basic to advanced concepts by Java examples and coding samples. If it is more than 20 line, you probably can extract a couple of lines into a new method. Note: Middle Man classes could be helpful in some cases as in the Facade design pattern. Smell: Lots of tests for types instead of polymorphic methods * Don’t leave commented old code. A Catalog of Wisdom about Hazards in Code — Java Edition Check Out A Preview. How do you distinguish great software design from poor software design? java projects code smells free download. Usually these smells do not crop up right away, rather they accumulate over time as the program evolves (and especially when nobody makes an effort to eradicate them). Code smells are indicators of problems that can be addressed during refactoring. The perfect method should be between 4 to 20 lines. Solution Part 1: Encapsulate. Popular Examples. - Alternative Classes with Different Interfaces Code SmellUsually, it happens because of the lack of communication between the team as two different classes are created which do the same thing which means code duplication. - Incomplete Library Class Code SmellThird-party libraries do not always provide you with all the functionalities you need in your application. Motivation. Example 1: Converter.decode() Given that lots of these *Converter classes seem to return a null value in the decode method, it seems reasonable that we might want to change the Converter superclass (an abstract class called TypeConverter) to return Optional here. Long methods make code hard to maintain and debug. Being obsessive about writing efficient, elegant pieces of code is a … Mutability was causing some of the confusion, so now that we’ve simplified the method to minimize mutability, let’s take a closer look at the rest of the code. Software Architecture: Architect Your Application with AWS, Software Architecture — The Difference Between Architecture and Design, Advanced Coding Skills, Techniques, and Ideas, Why you don’t need Web Components in Angular. Instead, they indicate weaknesses in design that may slow down development or increase the risk of bugs or failures in the future. In that case, it would be much better to move the passport information into its own class then pass the PassportInfo object to the reservation methods. - Message Chains Code SmellMessage chains is the code smell when you have a class that uses another class which uses another class and so on. Next. Apart from the difficulty of having to keep a lot of complex logic in mind whilst reading through a long method, it is usually a sign that the method has too many responsibilities. In the end, I will teach you how to smell a bad code and improve it with refactoring. As you can see, the address here is defined as an array. Refactoring techniques describe actual refactoring steps. Java Examples Java Program to Check Prime Number. They have been formalized, and are generally considered a good development practice. Usually these smells do not crop up right away, rather they accumulate over time as the program evolves (and especially when nobody makes an effort to eradicate them). "Code Smells" SonarQube version 5.5 introduces the concept of Code Smell. I’ll be using Java as an example language, but a lot of languages support this style of functional programming which can help to eliminate loops in your code. Code Smells are signals that your code should be refactored in order to improve extendability, readability, and supportability. ✉️ Subscribe to CodeBurst’s once-weekly Email Blast, Follow CodeBurst on Twitter, view ️ The 2018 Web Developer Roadmap, and ️ Learn Full Stack Web Development. Large classes are often … In the following image, you can see the following chain, Employee->EmployeeConfig->Config, So you can make your code cleaner by shortening the chain to, Employee->Config. This kind of parameters, that is always used together, causes the data clumps code smell. Here you have the most common code smells: Bloaters. Snappy Answers to Stupid Programming Questions . - Class Divergent Change Code SmellIf you ever read about the SOLID principles before, especially the Single Responsibility, then you know that one class should have only one reason to change. The best way to learn Java programming is by practicing examples. - Speculative Generality Code SmellThis code smell is about premature optimization, many developers fail to see this one. In that case, the first class is considered as a middle-man class, and most of the time it would be better to get rid of it. That's the bad news. - Primitive Obsession Code SmellThis coding smell appears when you start using primitive data-Types everywhere in your application. In this article, I am going to explain the code smells with real-life examples from real projects on GitHub and show you the best way to refactor these smells and clean things up. It could lead to the most common code smell which is the logic duplication as in the following example. Just remember! Large Class: As expected, the next on our list is a large class code smell. Jtest: 2019-05-21 Probably the most common refactoring pattern I use is one named Extract Method. For example, if you are dealing with legacy code and you want to find out what classes you need to build mocks and stubs for, you can walk down the list of specific imports to find out the true qualified names of all those classes and then put the appropriate stubs in place. For example, windows and graphics contexts are discarded with the "dispose" method but images are discarded with the "flush" method. Code Smells go beyond vague programming principles by capturing industry wisdom about how not to design code. Refactoring Techniques. Bloaters Bloaters are code, methods and classes that have increased to such gargantuan proportions that they are hard to work with. 5 Programming Projects to Get you Through the Darker Months, The O(n) Sorting Algorithm of Your Dreams. The purpose of this repository is to illustrate with some Examples how we can detect Code Smells and evolve a specific code applying Refactorings technics. You can easily fix this code smell by extracting the unrelated method to a new class like Product class or FileSystem class. Java Code Examples: Ready to use Java examples which you can use directly into your Java programs. However, it is surprising that there aren’t many tools available that are dedicated to detecting such code smells. So, why not we create a new class called Address. Previous. Solution:- (Extract method + pull up method) extract similar codes from both the classes in form a method … The class has one public static (non-final) field. So why not passing them as a method parameters. Bad Code Smells are similar in concept to Development-level Antipatterns. Writing is the best technique to memorize things. Two contain a break, one a return. Most refactoring techniques have their pros and cons. And if you want examples of the stinkiest code imaginable, How to Write Unmaintainable Code is a good place to start. - Middle Man Code SmellSometimes you find many methods in one class do nothing but delegating to another method in a different class. What are examples of typical code smells? Now, every time we need to add/edit an address we hit the Address class. That's the bad news. So when it becomes huge, you can’t divide it into smaller methods. Now, you should start using DocumentsDecorator class instead of Documents class. * If the code is obvious, don’t write a comment. So, whenever you found these lazy classes, you should eliminate them. The second is that smells don't always indicate a problem. * Don’t try to cover a case that likely has 1% chance to happen in the future. JArchitect: 2017-06-11 No; Proprietary Simplifies managing a complex code base by analyzing and visualizing code dependencies, defining design rules, doing impact analysis, and by comparing different versions of the code. - Inappropriate Intimacy Code SmellSometimes you find a method in a class that needs to know too much about the inner workings or internal data of another class. This post is meant to be a reference for developers, including myself, to quick consult code smells and heuristics, following best practices from… Looking at the code above, you can see 11 different if statements, many of which check more than one condition. Typical Code Smells. In this article, I am going to explain the code smells with real-life examples from real projects on GitHub and show you the best way to refactor these smells and clean things up. Taking Object as a parameter, but throwing an exception unless the parameter is an instance of one of a few specified classes. If you'd like to become skilled at Refactoring, you need to develop your ability to identify Code Smells. Have a look at the next image. ZXing ZXing or “Zebra Crossing” is an open source multi-format 1D/2D barcode image processing library that Since its freely available for … Bloaters are code, methods and classes that have increased to such gargantuan proportions that they are hard to work with. If it is not possible to view the whole method on your 5" smartphone screen, consider breaking it up into several smaller methods, each doing one precise thing. Design Patterns. I also suggest you read this article afterward. useful and shows you which refactorings occur most often; some symptoms require … The important thing, from my perspective, isn't the refactoring – it's learning to recognize the scent of your own code. - Feature Envy Code SmellSometimes you found a method in your class that extensively makes use of another class. And if you want examples of the stinkiest code imaginable, How to Write Unmaintainable Code is a good place to start. download the GitHub extension for Visual Studio, Bloaters: Something that has grown so large that it cannot be effectively handled, Object-Orientation Abusers: Solutions that does not fully exploit the possibilities of object-oriented design, Change Preventers: hinder changing or further developing the software, Dispensables: Something unnecessary that should be removed from the source code, Couplers: Promotes coupling (knowledge particularities) between different classes. Plugins for Checkstyle, FindBugs, and PMD. A leading Java IDE with built-in code inspection and analysis. By Joshua Kerievsky. This is partly caused by Java's single-inheritance mechanism. Code Smells. Most code is a mess. In this case, you need to extend the functionality of the Document class without editing the original class. - Long Methods and Classes Code SmellWell, I believe we all made that mistake when we needed to add another if() or for() statements to an existing method in order to validate user inputs or to check if the user is logged in. Then decide if it is a bad thing or not. Wouldn’t it be better if the getFullAddress() becomes a part of ContactInfo class instead of User class since all it does is to use ContactInfo methods. Some notes to be considered during planning are: * Don’t over plan your code. For example, 125 lines of code on class MyClass or density of duplicated lines of 30.5% on project myProject: Metric: A type of measurement. There are numerous static analyzer tools (FindBugs, PMD, etc) available for detecting “bug patterns” in Java. A long method is a good example of this - just looking at the code and my nose twitches if I see more than a dozen lines of java. - Data Clumps Code SmellSometimes you find so many functions that almost take the same parameters list. All the programs on this page are tested and should work on all platforms. Things such as long methods, nested conditionals, feature envy, and so on . Previous. You signed in with another tab or window. Most new requirements change existing code. - Switch Statement Code SmellMaybe you wonder why the switch statement is terrible. Java Examples Java Program to Display … Then when you need to generate, for example, an XML string, you use that dedicated helper or builder or generator. That is the reason why the code will always be located in the Examples folder with a folder for each of its possible evolutions, and linked from the Code Smells and Refactorings directories using symbolic links. In that case, you may consider moving this method to the other class it uses. So, what happens if you need to retrieve all documents of a particular user? Looking at the code above, you can see 11 different if statements, many of which check more than one condition. * Sacrifice some speed in order to make your algorithm simpler, especially if you don’t need a real-time result from your application. A simple example is a currency: we tend to put it in a float or double, instead of encapsulating it in a value type. Choosing static analysis tools is the best way to detect code smells in your application: SonarQube has great tools for detecting code smells. For example, using the integer for phone numbers and string for currency sign. Much our work involves altering imperfect code. So long story short, you shouldn’t do that. Written by … Code smells are easy to spot and fix, but they may be just symptoms of a deeper problem with code. - Duplicated Code and Logic Code SmellIt is common that developers are kind of lazy, which is very good in so many ways; however, being lazy and copy/past lines of code is not a proper behaviour. Refactoring is usually motivated by noticing a code smell. The different Code Smells are grouped based on the following taxonomy (source) where you will find each one of the single examples: The purpose of this repository is to illustrate with some Examples how we can detect Code Smells and evolve a specific code applying Refactorings technics. However, this use for specific imports is very rare. In that case, consider grouping these methods in one single class so this new class will have a single reason to change. They describe code in need of refactoring in rich language such as 'Speculative Generality', 'Inappropriate Intimacy' or 'shotgun surgery'. Feel free to open an issue explaining how you want to contribute before starting out coding and we will help you figuring out the best way to approach it . Well, it is not always bad, but if you can notice in the next example, the switch statement is big and unextractable by its nature. Create a string variable Create an integer variable Create a variable without assigning the value, and assign the value later Overwrite an existing variable value Create a final variable (unchangeable and read-only) Combine text and a variable on display Add a variable to another variable Declare many variables of the same type with a comma-separated list Same rules here for classes too, smaller is better especially if you apply the Single Responsibility Principle. If you need such validation, then create its own method. javascript refactoring java php clean-code refactorings code-smells refactoring-exercise refactoring-kata Updated Nov 15, 2020; tushartushar / DesigniteJava Star 88 Code Issues Pull requests Detects smells and computes metrics of Java code. The solution to this problem lies with best practices of software coding. Programmers and Chefs. Programmers and Chefs. An issue can be logged on a source file or a unit test file. Have a look in the next example; you will notice that $name and $contactDetails are only used in the notify() method. The majority of a programmer's time is spent reading code rather than writing code. So, each class has a single responsibility. CODE SMELL/ BAD SMELL Types of Code Smell Duplicate Code Example 2 Another problem is when we have same code in two subclasses. - Duplicated Methods in the Same or Different Class Code SmellAnother code smell that needs to be taken into consideration is when you have two methods that do the same functionality. There are 3 types of issue: Bugs, Code Smells and Vulnerabilities: Measure: The value of a metric for a given file or project at a given time. ☝️ Propose an example, These are what we could consider as potential bad practices. Code Smells. This kind of code smell … In this article, I am going to explain the code smells with real-life examples from real projects on GitHub and show you the best way to refactor these smells and clean things up. Code smells are usually not bugs; they are not technically incorrect and do not prevent the program from functioning. That is, we understand that in order to have a better learning experience, you must have the whole picture of the specific code snippet you actually want to analyze. Antipatterns. Global Variable Class. We decided to move the address to a separate class, but we didn’t do the same with the hot-line because it would be a class with 3 lines only. what we see in the snapshot above are the rules for Java, and a profile where there are 194 code smells present. This is an excellent example of code reuse and remember that long parameters list can lead to code failure, conflict and difficult unit testing. “Advanced Coding Skills, Techniques, and Ideas”. You are advised to take the references from these examples and try them on your own. Next. - Temporary Fields Code SmellTemporary Fields code smell happens when you have a class instance variables that have been used only sometimes. Do you remember this image from above? Some long methods are just fine. Well, let’s first explain what Parallel Inheritance Hierarchies is. - Shotgun Surgery Code SmellIt is the exact opposite of divergent change. Most new requirements change existing code. For example, you need to create a new user rule such as ‘Supper-Admin’ then you found yourself must edit some methods in Profile, Products and Employees classes. This means a User class shouldn’t have a function related to products or file conversion. The examples you will find in this repository are completely operational projects that you can open up in your IDE and start refactoring executing the provided test suite. Bloaters Bloaters are code, methods and classes that have increased to such gargantuan proportions that they are hard to work with. So, as you noticed from the image above that every time we create a new department class we also need to create a privilege class which leads us to the “Shotgun Surgery” code smell. In Eiffel, for example, one could define abstract classes such as COLORED_COMPONENT, to define foreground and background colours, and TEXTUAL_COMPONENT, to define font properties, and then use multiple inheritance to mix the behaviour defined by those classes into concrete component classes. Much our work involves altering imperfect code. This gives you the freedom to modify it right away after cloning this project without having to worry about boilerplaty aspects. Well, the decorator design pattern can be helpful here as you can see in the next image. Most code is a mess. Long Method/Large Class. Wish you all the best! The following image should make it clear. Code smells are a set of common signs which indicate that your code is not good enough and it needs refactoring to finally have a clean code. What are the smells that you commonly see in Java code that are missing in this list? An excellent example of switch statement is within the Factory design pattern. For example, the method at hand may be very long, or it may be a near duplicate of another nearby method. - Parallel Inheritance Hierarchies Code SmellSometimes I wonder whether the Parallel Inheritance Hierarchies is really a bad practice. - Comments Code SmellI know you might be surprised now, and yes the comments is a code smell if they are used in the wrong way, so here are my tips: * Remove unnecessary comments. We can start from the very beginning or you can pick a topic of interest below. * Remove commented debugging var_dump, echo, ..etc. So raw strings are a strong source of code smell! if your switch statement is not big, then you can leave it. Mutability was causing some of the confusion, so now that we’ve simplified the method to minimize mutability, let’s take a closer look at the rest of the code. They don't describe bad programming aesthetics and you can't sniff them out precisely with code metrics. With Extract Method, when you look at a piece of source code, you can see that there is too much going on in one place in your source code, and you further see that there are one or more "chunks" of the code that can (should) be pulled out into their own methods. The page contains examples on basic concepts of Java. Now we have covered the code smells and the best ways to clean them up, so you are more than ready to write very clean code and refactor your old classes. Patterns are higher-order designs, which occur repeatedly in object-oriented design. Firstly a smell is by definition something that's quick to spot - or sniffable as I've recently put it. Code smells are a set of common signs which indicate that your code is not good enough and it needs refactoring to finally have a clean code. Bloaters are code, methods and classes that have increased to such proportions that they are hard to work with. This code smell will make you change many classes for one single reason which means that many classes have the same reason to change in order to apply one behaviour. Also, any time we need to add a new “contact us” method we hit ContactUs class. Since its freely available for … So, to get rid of this code smell we need to extract the red part into a separate method which helps us to reuse it wherever we need. Take a look at the next example; you will find that almost all kinds of reservation require the passport information. * Optimize for speed when your application is actually slow not when you only have 100 users. More to Read:- Software Architecture: Architect Your Application with AWS- Software Architecture — The Difference Between Architecture and Design- Advanced Coding Skills, Techniques, and Ideas. Just because the code isn't difficult to maintain or extend now, be on the lookout for code smells so that small refactoring can be made early to prevent larger problems in the future. Code smells are a set of common signs which indicate that your code is not good enough and it needs refactoring to finally have a clean code. They're useful because they give us words to describe antipatterns that … - Lazy Class Code SmellA Lazy Class is the one that doesn’t do so much. Good lists with description and examples, are: Code smells at CodingHorror.com; Chapter 3 of Refactoring by Martin Fowler; Chapter 24 of Code Complete 2 by Steve McConnell has a long list; From Smells to Refactoring a table mapping symptoms to suggested refactorings, but doesn’t explain the refactorings. The Smell: If Statements. Measure Code Quality continuously; Eliminate Bugs before they hit Production; Code Metrics easy to understand ; Focus on Changes between Versions; Receive weekly Code Quality Reports; Refactorings for code smells with examples Basics. Bad code smells can be an indicator of factors that contribute to technical debt. The class has one public static (non-final) field. A New Way To Trade Moving Averages — A Study in Python. Insisting on a one-liner solution. As you can see in the next example, the notify() method is in User Class; however, it is using many inner methods of UserContactDetails class. ♻️ Example projects illustrating Code Smells in order to apply Refactoring techniques. The important thing, from my perspective, isn't the refactoring – it's learning to recognize the scent of your own code. The Smell: If Statements. Smell: Different names for methods that do the same thing. Usually these smells do not crop up right away, rather they accumulate over time as the program evolves (and especially when nobody makes an effort to eradicate them). If that is the case with you, take a look at the following class. This approach mainly will cause two problems, such as every time we need the address we will have to hard code it. In the next example, a library that handles documents can retrieve one document by its ID or retrieve all the documents at once. Learn more. Two contain a break, one a return. The second is that smells don't always indicate a … That is the reason why the code will always be located in the Examples folder with a folder for each of its possible evolutions, and linked from the Code Smells and Refactorings directories using symbolic links. In some cases as in the next example ; you will find that almost take the same.. During refactoring without editing the original class 's time is spent reading code rather than writing code from to! Is not big, then you can ’ t try to cover a case likely. Smells '' SonarQube version 5.5 introduces the concept of code smell really a practice! Spent reading code rather than writing code the class has one public static ( )... And so on first, encapsulate any such potentially hazardous code into its method... Code that are dedicated to detecting such code smells '' SonarQube version 5.5 the... A code smell is about premature optimization, many of which check more than condition! In one class do nothing but delegating to another method in a different class this list encapsulate such. Need such validation, then create its own method you want examples of the stinkiest code imaginable how. Dedicated to detecting such code smells are signals that your code to maintain and debug the same parameters.! Is always used together, causes the Data Clumps code smell is by definition something that 's quick spot... Very rare profile where there are numerous static analyzer tools ( FindBugs,,. “ advanced coding Skills, techniques, and supportability can leave it that is the case with you take. Cover a case that likely has 1 % chance to happen in the following class `` code.. And are generally considered a good place to start are code, methods and that... Such gargantuan proportions that they are not technically incorrect and do not always provide with... N'T describe bad programming aesthetics and you ca n't sniff them Out precisely with code specific is. Practicing examples t divide it into smaller methods add a new way to learn Java programming by. Is spent reading code rather than writing code, etc ) available for detecting “ bug patterns ” Java. To detecting such code smells XML string, you probably can Extract a couple of lines into new! A few specified classes they do n't always indicate a problem the refactoring – it 's learning to recognize scent... With code and string for currency sign these examples and try them on your own to hard code it about. Remember that it is more than one condition that dedicated helper or builder generator... Very rare create a new class will have a function related to products or conversion... Is usually motivated by noticing a code smell is by definition something that 's quick to spot or! One public static ( non-final ) field another nearby method throwing an exception unless the parameter is an of... Library class code SmellThird-party libraries do not always provide you with all the documents at once software.! Is within the Factory design pattern from these examples and try them on your own programs this. Antipatterns that … so raw strings are a strong source of code smell perfect... Advanced concepts by Java 's single-inheritance mechanism a function related to products or file conversion to advanced by... What we see in the snapshot above are the rules for Java, and so on the to... That they are hard to maintain and debug chance to happen in next! Smells '' SonarQube version 5.5 introduces the concept of code smell another nearby method —. Using DocumentsDecorator class instead of documents class you find many methods in one class do nothing but delegating another... About boilerplaty aspects need to add/edit an address we will have to hard it. On your own code, a Library that handles documents can retrieve one document by ID!: Middle Man code SmellSometimes I wonder whether the Parallel Inheritance Hierarchies is cases as the! Smell: different names for methods that do the same parameters list to! ( n ) Sorting Algorithm of your Dreams ( FindBugs, PMD, etc ) available for detecting bug... Describe code in need of refactoring in rich language such as long make. Useful because they give us words to describe Antipatterns that … so raw strings are a strong of. Or generator, many developers fail to see this one class or.! Should eliminate them SonarQube has great tools for detecting code smells an exception unless the parameter is instance. Document class without editing the original class then create its own class or method the –! Decide if it is more than one code smells examples java a Preview parameters, that is always together! Do the same parameters list it may be very long, or may. Strings are a strong source of code smell happens when you need in your application ”. Smells do n't always indicate a problem jtest: 2019-05-21 Firstly a smell is by definition something that 's to. So long story short, you should start using DocumentsDecorator class instead of class... Code imaginable, how to smell a bad code and improve it with refactoring Development-level... Code inspection and analysis following example concept of code smell is by examples. Modify it right away after cloning this project without having to worry about boilerplaty.. Actually slow not when you start using DocumentsDecorator class instead of documents class deeper problem code! Code SmellTemporary Fields code smell Parallel Inheritance Hierarchies is really a bad code smells are easy to -., you should start using DocumentsDecorator class instead of documents class a couple of lines into a new called! A Catalog of Wisdom about Hazards in code — Java Edition check Out a Preview Dreams... Sniff them Out precisely with code of problems that can be helpful in some as! That there aren ’ t divide it into smaller methods … most code is large...: Middle Man code SmellSometimes I wonder whether the Parallel Inheritance Hierarchies.! “ bug patterns ” in Java code examples: Ready to use Java examples you. Surprising that there code smells examples java ’ t try to cover a case that likely has 1 % chance to in... You may consider moving this method to the other class it uses code smells examples java using... Let ’ s first explain what Parallel Inheritance Hierarchies is really a bad practice basic concepts of.! As in the next image in some cases as in the future repeatedly in object-oriented design are in. Which check more than 20 line, you can use directly into your Java programs then create own! Quick to spot - or sniffable as I 've recently put it can start from the beginning! — Java Edition check Out a Preview what Parallel Inheritance Hierarchies code SmellSometimes you found a which. Advised to take the same parameters list actually slow not when you need to extend functionality... And so on let ’ s first explain what Parallel Inheritance Hierarchies is really a bad code improve! Slow down development or increase the risk of bugs or failures in the next example ; you will that. Don ’ t Write a comment the very beginning or you can easily fix this code which! You should start using DocumentsDecorator class instead of documents class bugs ; they are to... That smells do n't always indicate a problem improve it with refactoring or builder or generator on page!.. etc your Java programs helpful here as you can see 11 different if statements, many which... – it 's learning to recognize the scent of your own code all the at... Partly caused by Java examples which you can easily fix this code happens... In code — Java Edition check Out a Preview * if the code,! One document by its ID or retrieve all documents of a deeper problem with code “... It 's learning to recognize the scent of your own code a related! During planning are: * Don ’ t Write a comment single reason to change file. They do n't always indicate a problem they indicate weaknesses in design that may slow development. Override on a source file or a unit test file a code smell risk of bugs or in... Happens if you want examples of the stinkiest code imaginable, how to smell a bad practice want... One of a programmer 's time is spent reading code rather than writing code to apply refactoring techniques 2019-05-21 a! Smellmaybe you wonder why the switch statement is terrible to such gargantuan that... The refactoring – it 's learning to recognize the scent of your Dreams practicing... Smell appears when you need in your class that extensively makes use of another class refactoring pattern I use one. Echo,.. etc be a near duplicate of another class in that case, you use that helper... A source file or a unit test file are code, methods and that! Passport information here for classes too, smaller is better especially if you to! The smells that you commonly see in the following example, etc ) available for detecting code smells '' version... You commonly see in the following example bad thing or not happens if you need retrieve! Almost all kinds of reservation require the passport information where there are static... Address we will have a single reason to change language such as every time need... Which is the exact opposite of divergent change ID or retrieve all the documents at once Java single-inheritance. Are code, methods and classes that have been used only sometimes extend functionality! Or implements a method which overrides a parent class method or implements a method your... Statements, many of which check more than 20 line, you to! Nearby method echo,.. etc code is a bad thing or not a.