## Introduction

Java is a high level, general purpose programming language, developed by James Gosling at Sun microsystems (later acquired by Oracle) in 1995. Currently Java is maintained by Oracle.

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Java finds many uses out in the wild, here is a non-exhaustive list:

·        Mobile applications - Android

·        Complete web applications, web servers (Spring, Dropwizard, Vert.x, etc.)

·        Desktop applications (not as popular of a choice as it once was)

·        Video games like Minecraft

·        Big data technologies like Hadoop and ElasticSearch

·        And much more…

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## How Java works?

Computers work by interpreting and executing instructions given by the programmer, at the lowest level these instructions are represented using bits (ones and zeroes) that computers are able to interpret.

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Writing programs by stringing a bunch of ones and zeroes is very tedious and error prone work, hence computer scientists have worked at abstracting away this tedious work using natural language words.

Programming languages that closely resemble human languages are called high-level programming languages.

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This abstraction and resemblance to human languages is at the core of Java, led by the idea that code is read more often than it is written.

Naturally, the closer a programming language is to a human language, the harder it is for the computer to understand the code, so we need to translate this code in to something that the computer understands.

Cue in the compiler, the compiler is essentially a translator for human readable code to machine readable code, in Java’s case this machine readable code is bytecode, and that bytecode is stored in a file with the same name as the .java file but with a .class extension.

This extra step of compiling (translating) the code makes Java a so called compiled language.

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Another core concept of Java is write once, run everywhere, this emphasizes the languages ability to work on multiple different platforms like Windows, Linux, macOs and others.

What enables Java to be written once and be run everywhere is the JVM (Java virtual machine).

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The JVM is the middle man between compiled Java code and the computer, making it yet another translator, but it’s role is different than the compiler, while the Java compiler translates Java code in to bytecode, most computers still don’t understand bytecode, in fact different types of computers understand different type of machine code, this is what makes the JVM special, the JVM know how to translate the bytecode to the specific machine code that the computer understands.

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What is Java

To be able to write and run java code you would need to download and install the Java Development Kit (JDK).

There are several ways to download and install the JDK, the recommended and most popular one is:

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AdoptOpenJdk – link <https://adoptopenjdk.net/>

Other alternatives include

Amazon Correto - <https://aws.amazon.com/corretto/>

Azul - <https://www.azul.com/downloads/zulu-community/?package=jdk>

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We recommend downloading an LTS (Long Term Support) version of the JDK. Instructions on the installation can be found on each of the alternatives’ respective web sites.

Next you need something to write your code in. Java does not have any specific requirements on how to write it, you could go as simple as using a text editor, but we recommend using an IDE (Integrated Development Environment), IDEs are software that helps you write code easier by providing numerous features like code completion and syntax highlighting.

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We recommend using Intellij IDEA community - <https://www.jetbrains.com/idea/download/>

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Other alternatives include:

Eclipse - <https://www.eclipse.org/downloads/>

Netbeans - https://netbeans.apache.org/download/index.html

VSCode - <https://code.visualstudio.com/download>

Installation instructions can be found on each of the IDEs’ web sites.

Java installation and IDEs

Introduction and basic concepts

Introduction to Java, a multi-purpose programming language.