Introduction to Java

By Fernando Ventura - 10/28/2022

JAVA was developed by James Gosling at Sun Microsystems Inc in the year 1995, later acquired by Oracle Corporation. It is a simple programming language. Java makes writing, compiling, and debugging programming easy. It helps to create reusable code and modular programs. Java is a class-based, object-oriented programming language and is designed to have as few implementation dependencies as possible. A general-purpose programming language made for developers to write once run anywhere that is compiled Java code can run on all platforms that support Java. Java applications are compiled to byte code that can run on any Java Virtual Machine. The syntax of Java is similar to c/c++. Source: geeksforgeeks.org

Installation

For using Java, the first step is to install the Java Virtual Machine (a.k.a. JVM), this is part of the Java Development Kit (a.k.a. JDK)

Windows

You can use Eclipse's Temurin, go to this website and download the .msi installer, installation is straight forward, just click next and next until the JDK is installed, at the end, reboot your machine.

To verify that the installation went well, open a terminal (Command Prompt), and type:

    java -version

You should see something similar to this:

Please note that in my case I have installed Graalvm JDK, because I need it for working in more advanced projects.

MacOS /Linux

Use the platform package manager for installing the proper JDK, for example:

MacOS:

    brew install openjdk@17

Debian based, like ubuntu:

    sudo apt update && sudo apt install openjdk-17-jdk openjdk-17-jre

Topics covered in this introduction

• Language Syntax (Hello World)
• Types
  • Primitive
  • Custom (classes)
• Conditional flow
  • If
  • Else-if
  • else
  • switch
  • while loop
  • do-while loop
  • for loop
  • enhanced for loop ( see. Polymorphism.java at line 24).
• Object-Oriented Programming (OOP)
  • Inheritance
  • Encapsulation
  • Polymorphism
  • Abstraction. (Using an interface to achieve the same logic as in the Polymorphism class)

Next steps

• Read the Javadoc during development, so you get a better understanding of Java itself. Javadoc.
• If you have doubts, Google is your best tool, but try to search using English only, at least use keywords if you don't know English at all.
• At the beginning it's ok to copy code from Stack Overflow, but if you do, try to understand the piece of code that you are integrating in your project.
• Watch the same course I followed in the past to learn java: Curso de Java - Píldoras Ínformaticas