This content originally appeared on DEV Community and was authored by Rijul Rajesh
If you are coming from JavaScript, Python, or other ecosystems, you might be familiar with installation commands like npm install package-name or pip install package-name. These commands directly fetch packages from a registry and install them into your project. Java handles library dependencies differently, and understanding this difference is important for Java or Android development.
Java Dependencies
In Java, libraries are typically distributed through Maven Central or other artifact repositories. A library is not installed via a command-line instruction. Instead, you declare the library in your project’s build configuration. The build tool then downloads and includes the library in your project during compilation.
Example: EventBus Library
EventBus is a popular library for event-driven programming in Java and Android. To use it in your project, you do not run a terminal command. Instead, you declare it in your build file.
Gradle for Android
In an Android project using Gradle, you would add the following in your app/build.gradle file:
dependencies {
implementation("org.greenrobot:eventbus:3.3.1")
}
This line tells Gradle to download EventBus version 3.3.1 from Maven Central and include it in your application when building.
Gradle for Java Projects
For a plain Java project, you can use a slightly different artifact:
dependencies {
implementation("org.greenrobot:eventbus-java:3.3.1")
}
The difference here is that the eventbus-java artifact is intended for Java-only projects without Android-specific dependencies.
Maven
If you use Maven instead of Gradle, you declare the dependency in your pom.xml file:
<dependency>
<groupId>org.greenrobot</groupId>
<artifactId>eventbus-java</artifactId>
<version>3.3.1</version>
</dependency>
Maven will handle downloading and linking this library automatically.
How This Differs from Other Package Managers
No direct command-line installation
Unlike npm install or pip install, you do not type a command to download the library. Instead, you edit a configuration file, and your build tool downloads it when you build the project.
Build tool dependency
Java libraries require a build tool to manage dependencies. Gradle and Maven are the most common. These tools also handle transitive dependencies, which means if your library depends on other libraries, Gradle or Maven will automatically include them.
Project-centric
Dependencies in Java are tightly tied to the project. They are downloaded into a local cache and compiled into your project, rather than installed globally or system-wide.
Post-installation considerations
Some Java libraries, especially for Android, require additional steps such as:
- Including ProGuard or R8 rules to avoid issues with code shrinking
- Configuring annotation processors for better performance
EventBus, for example, provides a subscriber index to avoid reflection-related performance issues.
Wrapping up
Java handles dependencies differently from languages like JavaScript or Python:
- Libraries are declared in build configuration files instead of installed via terminal commands.
- Gradle or Maven handle downloading, caching, and linking dependencies.
- Post-installation configuration may be required for Android projects.
Understanding this difference makes it easier to work with Java and Android libraries, and ensures your projects are correctly configured with all required dependencies.
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This content originally appeared on DEV Community and was authored by Rijul Rajesh