What is Java?

Java is an open source programming language and runtime designed for universal applications that run on any platform. For programmers, that means code only needs to be written once, and all maintenance is done on the same code base. For users, it means there's no anxiety over whether an application runs on their OS because, as long as their OS runs Java, the answer is a resounding *yes*.

How to run a Java applications

To run a Java application, you must have a Java runtime environment (JRE) installed. Because Java is open source, there isn't just one JRE, so you can choose the JRE that best suits your needs. Linux distributions typically provide an OpenJDK or IcedTea JRE. Windows users can download a JRE installer from

developers.redhat.com

. Mac (and Windows and Linux) users can also download JRE installers from

openjdk.java.net

or the

Zulu

community at Azul.

It's because the JRE you've just installed has been created specifically for your OS that any Java application can run on your computer. By

installing

Java, you provide your system with a layer (technically a Java virtual machine, or JVM) upon which any Java application can run.

How to program in Java

Java is an object-oriented, strongly typed language, and is popular in nearly all industries from financial to publishing to IT. Because it is natively cross-platform, its audience is vast. The basic programming courses offered by many universities start with Java because it enforces best practices (such as scoping and variable typing) that other languages, such as Python or Go, permit the programmer to mostly ignore. Java is popular and old enough that it has libraries for nearly any task, so even a beginner programmer has access to a rich set of ready-to-use methods.

If you're developing in Java, you must install a Java development kit (JDK). There are several to choose from, including

OpenJDK

and

Zulu

(a JDK includes a runtime environment (JRE) so you can run the applications you develop).

There are many entry points into getting to know Java. If you prefer a fun introduction, you can try

Greenfoot

, an interactive development environment designed for Java education. Greenfoot helps a new coder create games and fun applications with an easy graphical interface.

A step up from Greenfoot is

BlueJ

, a Java IDE designed by King's College in London as a verbose and helpful IDE that highlights important elements of code as the user programs.

In the real world,

Eclipse

is one of the most popular and capable Java programming environments. It helps manage libraries, resolve mistakes and conflicts in your code, assists in debugging, packaging, and much more. For development teams,

Eclipse Che

provides a shared cloud-based workspace, ensuring that everyone on a project is using the same environment.

The future of Java

Java was originally developed and supported by Sun Microsystems, and is now supported by Oracle. However, Java is open source and has a worldwide community invested in guiding its continued development and growth. The use cases for Java may change over the years, but its focus and mantra have persisted: *write once, run anywhere*.