Java Guide
Java is an object-oriented programming language developed by Sun Microsystems (now owned by Oracle Corporation) in 1995. It’s high-level, meaning code in its language is easier to read and write and abstract enough to allow for cross-platform compatibility. Its platform independence means Java code can run on any device, such as a computer, with a Java Virtual Machine (JVM) installed. Java is a popular choice for open-source software development.
Java Components
Java is made up of various components that have specific functions. The following are the essential Java components.
Java Development Kit - JDK
The tools Java developers use to create Java apps.
Contains:
- JRE
- JVM
- and more
Java Virtual Machine - JVM
The runtime environment in which Java bytecode (.class files inside .jar files) is interpreted and executed. The JVM is also responsible for managing memory, garbage collection heap, and more. Java as a platform is platform-independent (.jar files will run on any JVM), but each JVM is written for the system it’ll be running on (Linux, macOS, Windows).
Contains:
- JRE
- Java tools like a compiler and debugger
- and more
Java Runtime Environment - JRE
The software package contains a JVM and other libraries required to run Java on a computer or device.
Contains:
- JVM
- Java API
Java API
The pre-written Java code (classes, interfaces, and methods) for developers.
For example, the java.lang package contains fundamental classes and interfaces like Object, String, Integer, Boolean, and various exceptions like ClassNotFoundException.
There are more advanced things related to time, regex, and much more too.
Versions
The current versioning system of Java is based on a release model including both LTS (Long-Term Support) and non-LTS releases.
Non-Long-Term Support - Non-LTS
Oracle releases a new non-LTS Java version every six months including new features, improvements, and bug fixes. When a new non-LTS is released, the old one will no longer be supported. No support means there won’t be additional updates or fixes for that version.
Long-Term Support - LTS
Oracle aims to release a new LTS Java version every two years that only receives quarterly security, stability, and performance updates. LTS releases lag behind in gaining the latest non-LTS features but make up for it in increased stability and extended support.
An up-to-date timeline for LTS and non-LTS versions of Java can be viewed on Oracle’s website.
More about versions here.
Vendors
While Oracle is the primary owner and developer of the Java programming language and platform, other companies and communities develop and or package their versions of Java. Most will use those alternative versions for better performance or because it doesn’t come with Oracle’s restrictive licensing.
I suggest you use Adoptium.
The Eclipse Temurin binaries are provided at no cost to you by Adoptium to use, forever, under the terms of the “GNU General Public License, version 2 with the Classpath Exception”. You may freely use, modify, and share the code as described in the licenses included in the download. — Adoptium FAQ
How To Install
Vendors provide different installation instructions for each operating system. Generally, one must download and install a file through their operating system’s software manager. The following are popular options.
| Vendor | Download Instructions |
|---|---|
| Oracle | https://www.java.com/en/download/help/download_options.html |
| Adoptium (formerly known as AdoptOpenJDK) | https://adoptium.net/installation/ |
| Microsoft Build of OpenJDK | https://learn.microsoft.com/en-us/java/openjdk/install |
| Amazon Corretto | https://aws.amazon.com/corretto/ |
| Azul Systems | https://www.azul.com/downloads/ |
Managing Java
Arch Linux
Arch has a built-in tool for managing Java versions called archlinux-java.
Developing With Java
Integrated Development Environment - IDE
While one could write Java software using a plain text editor, almost everyone uses an IDE because they vastly improve the development experience.
Common IDE features:
- Code completion
- Suggests code snippets or method names as one types, based on the context of the code, such as the class or object being used, the expected return type, or the available parameters.
- Automatic formatting
- Real-time error checking and highlighting
- Refactoring Tools
- Code Analysis Tools
- Build Tools
- Debugging Tools
It is strongly suggested to use an IDE when developing with Java. The following are popular options.
| Developer | IDE Name | Download Instructions | Price |
|---|---|---|---|
| JetBrains | IntelliJ IDEA Ultimate | https://www.jetbrains.com/idea/download | Paid |
| JetBrains | IntelliJ IDEA Community Edition (recommended) | https://www.jetbrains.com/idea/download | Free |
| Eclipse Foundation | Eclipse | https://www.eclipse.org/downloads/packages/installer | Free |
| Apache | NetBeans | https://netbeans.apache.org/download | Free |
| Microsoft | Visual Studio Code | https://code.visualstudio.com/download | Free |
Java is Functionless
A function is generally a reusable block of code that performs a specific task. In many programming languages, functions can exist independently of classes. However, in Java, all code must be contained within a class, and what other languages might call “functions” are referred to as “methods” in Java. Methods are similar to functions but are always associated with a class or object. Therefore, in Java, methods serve the role that standalone functions do in other languages.