Table of Contents
Here we’ll take a look at one of the hallmarks of object-oriented programming, loose coupling, and how it can benefit your Java application and help you avoid some of the common pitfalls that have led to some of the greatest failures in software history. Loose coupling refers to the act of keeping classes that interact with each other independent while maintaining their ability to work together. If done correctly, it can ensure that one class isn’t reliant on another, so if something happens to change in the way another class works, you don’t need to worry about it affecting anything else. When you are writing Java programs, it’s necessary to structure your code in such a way that it’s easy to change. This may sound complicated at first, but it’s actually pretty simple once you understand the concept of loose coupling.
If you’re looking to build Java applications and want to understand loose coupling, you’ve come to the right place! In this article, we will explore what exactly loose coupling is and what benefits it can provide to your code. In programming, loose coupling refers to the design principle of decoupling the implementation of the software from its environment so that the implementation can be used in different contexts without being changed. The term was coined by David Parnas in his seminal paper on software engineering ”On the Criteria To Be Used in Decomposing Systems into Modules” (1972). In this paper, Parnas argues that modules should be loosely coupled, i.e., that their internal structure should be shielded from other modules, and also suggests design principles to achieve this goal. Loose coupling can be helpful when you need to make changes in your code. When components are loosely coupled, one component does not depend on another component to function and so can be more easily changed or even replaced with something else entirely. The opposite of loose coupling is tight coupling, where components are highly dependent on each other and can’t be changed without completely reworking the application as a whole.
1) The Importance of Objects Being Independent
In object-oriented programming, loose coupling is an important concept because it allows components to be changed or replaced without requiring changes from other components. Consider a chair made of Legos. The legs are connected only by hinges; therefore, if you want to change or replace one leg, you can do so without changing any other components. However, imagine that instead of individual Lego pieces, there were huge Lego blocks on each corner with no way of separating them from one another. Now imagine that if you wanted new or different legs for your chair, those blocks had to be reshaped and replaced as well! This would be extremely difficult to accomplish and would require replacing every single component of your chair at once. This is what happens when objects aren’t independent—they’re dependent upon other objects—and it’s called tight coupling. When objects are dependent upon one another, they’re said to have tight coupling, which means they’re more difficult to change or replace than if they weren’t dependent upon each other at all. To create loosely coupled code, we need to make sure our methods don’t rely on specific implementations (classes) when calling other methods within our codebase. We also need to make sure our classes don’t rely on specific implementations when creating their own methods. Instead, we should pass around interface types like java.util.List , java.util.Map , etc., rather than concrete types like ArrayList. Doing so will allow us to change our implementation details without affecting other parts of our application that may depend on these interfaces. If you’d like a deeper dive into how loose coupling works in practice, check out my free course on getting started with functional programming.
2) Dependency Injection
Dependency injection is an object-oriented software design pattern that allows you to decouple an application’s dependencies from its concrete implementation, which improves flexibility and reusability. In basic terms, dependency injection means that when your program has a dependency (such as a third-party library), it will have no trouble using it because that dependency is injected into it, instead of having to look for it itself. A good way to understand how loosely coupled systems help make code more reusable is through an example. Here we’ll take a look at two versions of one simple method—one with loose coupling and one without—and discuss how each version affects reusability. The first version shows how not to write your code: This example uses hardcoded strings to instantiate different components. This makes it very difficult to reuse our program elsewhere; if we wanted to do so, for instance, if someone else wanted us to use our add function in their system, they would need access to all of our source files and libraries just so they could plug them into our code. The second version uses what looks like procedural programming but is actually dependency injection at work:
Now there are only three classes involved; everything else can be swapped out simply by passing in new values for _firstName, _lastName, _city, etc., depending on what functionality is needed where. This version of our code is much more flexible and reusable, as it doesn’t rely on any hardcoded strings or other specific values. It’s easy to see how dependency injection could make your code more flexible and reusable, but it also has some other benefits that you might not expect. For example, because all dependencies are injected at runtime instead of being hardcoded into a class definition, they can be changed or updated without affecting any other part of your program—meaning you don’t have to worry about breaking something when you make a change like that. This makes your application easier to maintain and debug because if one piece of code breaks, it won’t break anything else—you just need to fix that one piece.
3) The Liskov Substitution Principle
According to The Liskov Substitution Principle, a subtype should be able to substitute for its supertype in any context without breaking that context. For example, if a Car is-a Vehicle, then a MiniVan is-an Car. If I have an instance of Vehicle (my car), then I should be able to pass it around as if it was any type of vehicle (for example, myCar.drive()); however, if I have an instance of MiniVan and try passing it around as a Car nothing breaks or changes. This concept requires that methods and properties on classes shouldn’t alter their inputs; instead, they must only alter their outputs. This means that you can change parts of your system without having to modify anything else. For example, if you were using an interface called Vehicle with a concrete class called Car and another concrete class called Truck, but later wanted to replace Truck with something else like RV, all you would need to do is implement your new class’ drive() method while leaving everything else alone. As long as you didn’t change what parameters are expected by those methods, everything would continue working fine because those parameters wouldn’t affect how things work internally at all! Using loose coupling will allow you to swap out components when needed which helps keep your code flexible so that it can evolve over time. It also makes testing easier because you don’t have to mock every single dependency in order to test one small part of your application. By keeping objects decoupled from each other, we can reuse them more easily and we don’t end up with giant spaghetti codebases that are difficult to maintain. That’s why decoupling is important – otherwise, every little thing might break just because some other little thing changed. We want our systems to be more robust and less fragile!
4) The Interface Segregation Principle
A class that depends on too many others is tightly coupled. It’s hard to modify, as you can’t take one without affecting a whole host of other classes, and it’s hard to reuse because that same tight coupling applies. Independent clauses can be used together; they just don’t rely on each other. The more independent your classes are, the easier you make it for your code to change over time. This is where loose coupling comes into play. If two classes aren’t coupled, you can use them together without worrying about what else might be going on with either of them. If two classes are loosely coupled, their relationship is like a partnership—they share information but aren’t dependent on each other. Any changes made to one won’t affect the other (and vice versa). This makes both easy to change independently when necessary—one doesn’t have to wait for any kind of approval or even communication from its partner before making changes. If there’s no dependency between two pieces of code, they’re loosely coupled. In Java terms, if there’s no direct reference between two objects or interfaces, then there’s loose coupling. There are several ways to achieve loose coupling in Java. One way is through inheritance, which allows a class to inherit all of its parent’s methods while only implementing those that it needs. Another way is through composition, which means an object contains another object and uses it as needed. For example, let’s say we want to create an Employee class that represents employees at our company. Our first instinct might be to model our employees after our CompanyModel class by creating an EmployeeModel subclass.
5) Remove Abstractions and Implementations
In many cases, creating an interface or abstract class that contains both method signatures and implementations is a good way to reduce dependencies on particular classes or libraries. For example, you might need some code that is only relevant when interfacing with a specific database. In situations like these, it’s best practice to create an interface or abstract class that encapsulates all of your database-specific code and provides access to it via a common interface. This makes it easier for future developers who use your project—they simply have more implementation options available to them, as well as greater flexibility should they need another implementation for their own requirements. It also makes it easier for you if you ever find yourself needing to switch databases—you can just remove your abstraction layer entirely and implement it directly from whichever library you choose.
By doing so, you’ll be able to take advantage of any new features and functionality that come along with that new database without having to rewrite your entire application. When dealing with an existing system that already has multiple implementations, try not to create yet another one. The point of loose coupling is to allow maximum flexibility; by introducing yet another layer into your system, you’re limiting its ability to adapt over time. Instead, make sure you understand how each piece fits together before starting development on your application (or at least research it thoroughly before diving in). You may even want to consider using two pieces from different systems rather than adding yet another one. Doing so will help keep things simple and avoid unnecessarily increasing complexity down the road. Also, remember that dependency injection tools such as Spring or Guice can help enforce loose coupling in your code by making it possible for modules within a system (or even separate systems) to function independently of each other.
6) Composition over Inheritance
Object composition is about creating specific objects (or instances) to support your application’s functionality. This is accomplished by composing new objects from existing classes and reusing these sub-components throughout an application. The phrase composition over inheritance can be confusing because it seems that you’re substituting one object-oriented principle with another, but composition and inheritance actually complement each other. Composition is generally superior to inheritance because it introduces loose coupling into your system design. In software development, loose coupling indicates a relationship between two parts of a system where they only depend on each other at run time; they don’t directly modify the internal or external state of each other. A loosely coupled component is easy to replace or remove without impacting any other components in your system. A tightly coupled component has dependencies on multiple components and changes made to one component will affect others. One way to improve coupling in your codebase is through dependency injection, which allows you to inject dependencies into an object rather than having them passed down through its hierarchy.
An alternative approach for improving cohesion within an application is through abstraction, which helps separate out concerns so that unrelated aspects of a program are handled by different modules instead of being mixed together within a single module. In addition to helping maintain loose coupling between modules, abstraction also makes it easier to reuse code across applications. Abstractions can be created by using interfaces, classes, or traits. For example, if you were building a library for accessing relational databases in Java then you might define an interface called Database Connection that all implementations would have to implement. To use your library, clients would create their own implementation of DatabaseConnection and pass that implementation as a parameter when calling methods on your library’s API. Since there aren’t any concrete implementations used within your library’s API then clients are free to choose whichever database driver works best for their needs—for example H2/Hibernate/MySQL/PostgreSQL—without needing to change how they interact with your library’s API.
7) Don’t Repeat Yourself
Loose coupling is an important concept within object-oriented programming that calls for separating an application into components or classes with minimal dependency on one another. While a thorough discussion of loose coupling would require much more space than we have here, we can briefly address key points around it by way of examples from one of today’s most popular programming languages: Java. The purpose of loose coupling is to create code that isn’t overly rigid and tightly coupled; i.e., you want your code to be more flexible so you can change and fix certain parts without running into conflicts or problems with other sections of your application. If a class has too many dependencies on others, then changes to those dependencies could cause unintended consequences elsewhere in your code. For example, if you were using java.util.ArrayList as part of your class but later decided to switch over to java.util.LinkedList instead (perhaps because LinkedList had some new features), then any dependent classes might break because they are still expecting ArrayList objects when they are handed LinkedLists instead—and vice versa! In order to avoid these sorts of problems, programmers should always strive for loose coupling between their various classes and components. In general, there are three ways to achieve such flexibility: abstraction, encapsulation, and information hiding. Let’s take a look at each in turn…
8) Dependency Lookup
Our application code should not depend on specific implementations. We want our business logic to be free of framework and library dependencies, or as close as possible. The reason for coupling is often for convenience — it’s easier to use a class that does everything we need than one that does just part of what we need and must be extended to do everything else. However, we’ll soon realize that writing more code comes at a cost — complexity . When we rely on classes and methods from external sources, including third-party libraries, our applications become dependent on their specific implementations. If a developer upgrades our dependency library with new features (or bug fixes), there’s no guarantee our application will still work properly. If we change or remove a method or property that our application depends on, then again, there’s no guarantee that our app will continue working correctly. Finally, if an update breaks something critical in our app because of changes made by a third party, then we have little recourse beyond manually fixing things ourselves — assuming we can even figure out how to fix them.
All these issues are evidence of tight coupling between different parts of your system; they all stem from relying too much on frameworks and other external code rather than using loosely coupled components instead. To avoid these problems entirely, you can create your own custom components instead of using off-the-shelf ones where appropriate. This way, you can ensure that your application has only the exact functionality it needs while also keeping each component small and simple. The best way to reduce coupling is through loose coupling. A component that’s tightly coupled relies on another component for data or functionality, whereas a component that’s loosely coupled doesn’t rely on another component for anything but provides its own data and functionality. In Java programming language terms, we call such objects classes rather than components, but conceptually they’re similar enough. Classes are created so as to be used by other classes without being tightly bound together; therefore, the loose coupling in java means having smaller classes with fewer responsibilities so as to limit interdependencies between them.
9) Independence among Class’s Responsibilities
The first key concept of loose coupling in java is class independence. This means that any given class is only dependent on other classes as much as absolutely necessary. Interdependence between classes represents tight coupling, where classes are completely reliant on one another and can’t operate without each other. Independent classes allow for easier code reusability. When you have a program with a lot of tight coupling, it becomes hard to reuse portions of your code for fear that it will break something else, because everything relies on one another too much and isn’t independent enough. So independent, loosely coupled parts are easier to reuse so long as they don’t rely on too many different parts at once. So try not to be redundant! Find ways to achieve similar results with less dependency instead. In general, it’s a good idea to avoid coupling whenever possible. It makes things more complex and harder to maintain or change down the road.
Coupling Between Objects’ Attributes: Loosely coupled objects also mean that their attributes (or data) aren’t directly linked either. This is a little bit more subtle than class independence, but it’s just as important. Let’s say you have two classes, each with its own attributes and methods. If they’re tightly coupled, then changing one attribute of one class will likely affect another attribute of another class without you realizing it—and change how both classes function together as a result. This can be really hard to debug and fix later on down the road if you’ve got a lot of interdependence between your classes’ attributes! By contrast, loosely coupled classes allow for greater flexibility when it comes to changes down the road because any given change doesn’t necessarily affect all other parts of your program or codebase.
10) Don’t Combine Singletons with Loose Coupling
If you’re wondering what loose coupling in java is, wonder no more. It’s a programming concept that allows programs, components or modules to interact with each other without knowing how they work or how they’re put together. You don’t have to look far online to find plenty of resources on how loosely coupled components should be developed. But there are also some bad examples out there—and it’s important not only for programmers but also for system administrators and project managers who use loosely coupled code and need it to function well. One example of a terrible practice that is often mentioned when talking about loose coupling in java has to do with singletons. The idea behind singletons is simple: They’re objects (or functions) that exist once per class loader, so all instances share one instance. In theory, singletons make sense because they reduce memory usage and allow access from anywhere in your application (for example, if you want to share configuration data). However, many people think singletons aren’t good because if any component needs updating or fixing across multiple parts of your application (for example, if you have an authentication service), then every single component using it will break at once. This can lead to cascading failures and major problems down the road as new versions are released. So, remember: Don’t combine singletons with loose coupling.
An application’s design reflects its intended purpose. In most cases, loosely coupled applications are easier to maintain and quicker to adapt, but if your app needs fast speeds or a streamlined workflow, you may need a more fixed framework. Keep your environment in mind before choosing an approach and build accordingly. Remember that loosely coupled systems have flexibility, and they’re easy to change; so while they might take longer than their structured counterparts at first, they’ll give you far more options down the road. And as we all know, loose coupling is good for any relationship! After reading through our comprehensive guide on what loose coupling means in Java, how it affects software development, and how to implement it properly throughout your project, you should be able to determine whether it’s right for your next project—or even just one section of it. Make sure you don’t sacrifice speed over quality with too much structure or attempt something overly ambitious without direction! Test out different approaches based on the toolsets you already use and listen carefully to user feedback when making changes (if possible). Good luck with incorporating these new elements into your projects; always remember that tight coding doesn’t always equal tighter structure! The post has been written by MobileAppDaily’s Expert Author Antoine Margiotta. If you are interested to learn new coding skills, the Entri app will help you to acquire them very easily. Entri app is following a structural study plan so that the students can learn very easily. If you don’t have a coding background, it won’t be any problem. You can download the Entri app from the google play store and enroll in your favorite course.