How to install Java in Ubuntu 16.04 LTS ?

Introduction

Java is a most widely used programming language. It was created by Sun MicroSystem in 1990s. To install it on the Ubuntu operating system, follow the following steps.

Introduction to Java

Java is an object-oriented, class-based, and high-level language that's created to have some implementation dependencies. Java code can execute on every platform without needing to recompile. Typically, Java applications are unified into bytecode that can execute on any JVM despite the basic computer architecture.

The Java syntax is the same as C++ and C but has some low-level features than both of them. Besides, the Java runtime offers dynamic capabilities (like runtime code changes and reflection) that are generally not available in compiled languages. Java was the most famous languages according to GitHub as of 2019, specifically for server-client web application with 9 million developers.

• The reference and original implementation of Java virtual machines, class libraries, and compilers were originally published by Sun Microsystems beneath proprietary licenses.
• In compliance with the blueprint of the Java Community Process as of May 2007, Sun Microsystems had relicensed almost all of its Java technologies beneath the GPL-2.0-only license.
• On the other hand, Oracle provides its HotSpot JVM, although the reference implementation (official) is the OpenJDK Java Virtual Machine which is open-source, free software utilized by almost every developer and is also the default Java Virtual Machine for most Linux distributions.
• The latest edition is Java 20 as of March 2023, while Java 8, 11, and 17 are the latest LTS editions.

Principles of Java

There were five main objectives in the establishment of Java, which are as follows:

• It must be familiar, object-oriented, and simple.
• It must be secure and robust.
• It must be portable and architecture-neutral.
• It must be dynamic, threaded, and interpreted.
• It must run with better performance.

Special classes of Java

• Applet

Java applet was a program embedded in many applications, generally on a web page shown in a web browser. Now, the applet API was deprecated in 2017 since Java 9 version.

• Servlet

Servlet technology offers web developers a consistent and simple mechanism to extend web server functionality and access older business systems. Java servlet is a server-side Java EE element that produces acknowledgments to requests through the client. It means producing HTML pages in acknowledgment of HTTP requests. However, there are several other classes of the standard servlet, e.g., for WebSocket communication.

• Swing

For the Java SE environment, Swing is a GUI library. It's possible to define a different feel and look from the pluggable look and feel Swing system. Clones of Motif, GTK+, and Windows are equipped by Sun. Also, Apple offers an Aqua feel and look for macOS. In Java SE 6, Swing addresses this issue by utilizing a more natural GUI widget design routine of the basic platforms where previous implementations of these feels and looks may have been treated as lacking.

• JavaServer Pages

JSP (JavaServer Pages) is a server-side Java EE element that produces acknowledgments to requests, generally to HTTP requests through clients. JavaServer Pages insert Java code inside an HTML page with some special delimiters %> and <%. A JavaServer Page is compiled for a Java servlet, an application of Java in its right when it's accessed the first time. Then, the produced servlet makes the response.

• JavaFX

JavaFX can be described as a software platform to create and deliver desktop applications and web applications that can execute around a range of devices. For Java SE, JavaFX is designed to substitute Swing as a GUI library, but since the 11th version of JDK, JavaFX hasn't been in the JDK and rather in an isolated module. JavaFX includes support for web browsers and desktop computers on macOS, Linux, and Microsoft Windows. JavaFX doesn't support native operating system feels and looks.

• Generics

In 2004, generics were included in Java as a component of J2SE 5.0. Prior to the generic introduction, all variable declarations had to be of a particular type. For example, it is an issue for container classes as there is no simple way to make a container that takes only specific objects. Either a container works on every subtype of an interface or a class; generally, an Object or a specific container class has to be made for all contained classes.

Generics permit type checking at compile-time without creating various container classes, all containing almost exact code. Some runtime exceptions are avoided from occurring by appearing compile-time mistakes in addition to running adequate code. It would type safe if Java avoided every runtime mistake from occurring.

1) Check Java Version

Before installing Java, we will check whether it is already installed or not. Use the following command.

If Java is not present, it will produce the following output.

Now, add ppa to the repository by using the following command.

2) Add PPA (Personal Package Archives)

It will produce the following output to the terminal.

After adding package, now, update package index.

3) Update Package Index

After updating, now install oracle installer.

4) Install Oracle JDK 8 Installer

This command will install a installer that further will install Java 8 to the system.

This command will produce the following output to the terminal.

Type 'y' and press Enter, it will download and configure Java in our system.

5) Check Java

Now, check once again, Java is present or not. Use the following command.

It displays Java version and other Java related informations to the terminal.

It means, Java has installed successfully.

Our system is ready to build and run Java applications.

Extra Info

If we have multiple versions of Java installed, we can see that using the following command.

For Java, we can use this command.

These commands will show Java installed path, priority info etc.

It asks for changing the current choice from the available Java versions installed.

For Java compiler, we should use this command.

This command shows the same information for the Java compiler.