Java Programming Language: Fundamentals

Learning Java is exciting because it has a large community of professionals, it is a solid language and it uses Object Oriented Programming, which is a very important programming paradigm that you will eventually want to learn.

The first thing you’ll want to do is choose a free Java IDE (integrated development environment). There are a few options, but let’s use the IntelliJ IDEA community version, which is free, complete and modern (an attractive user interface is also important).

While installing IntelliJ, let’s download the JDK (Java Development Kit), which allows us to write programs with the .java file extension. Currently, the stable version is JDK 12 and you will want to use this one.

Now, let’s create a new Java project in IntelliJ, in the project SDK list, if it is empty, click on new and add the Java path on your computer (where you unzipped or installed the JDK). Next, we want to create a project from scratch, without using templates or libraries. Name it something like Hello World.

In the project, in the src folder, let’s create a new class by right clicking and going to new. When using Java programming, there is a particular naming convention. In the Java class name, we will say something like: com.example.helloworld.HelloWorld.

Let’s take a step-by-step look at this:

• com: A convention is good to follow.
• Example: the name of the company. Of course, we don’t need to have a company to program in Java. Just use a name that encompasses the whole program. If your program is a tic-tac-toe game, then we would say tictactoe.
• Helloworld: the name of the package. We can view packages as groups of classes that together make sense. If we make a calculator, we might want a package for mathematical operations, so we might say calculator.operations.
• HelloWorld: The name of the class, in this case exactly called HelloWorld. If you are making a Pac-Man clone, this could be pacman.logic.ghost.

Finally, let’s write some code and analyze it as well.

By default, IntelliJ will generate something like:

package com.example.helloworld;

public class HelloWorld {

}

We have the path to our package without the class name, which is just below.

But, depending on how familiar you are with programming and object-oriented programming, you may be wondering what the public HelloWorld class means.

Public is an access modifier and in Java there are two more (private and protected). We use Public in classes and methods. Public means that other classes in the package can access this HelloWorld class. If you do not add Public and simply say HelloWorld class, the class will be public by default.

The next keyword tells Java that we are creating a class and the next is its own name for the class. For classes, the convention is to use PascalCase, that is, no spaces, hyphens or underscores, and capitalize the first letter of each word.

Now let’s complete this example:

package com.example.helloworld;

public class HelloWorld {

public static void main(String[] args) {

System.out.println(“Meow, world!”);

}

}

Now we add some code to that HelloWorld class. This is called a method, that is, a function within a class. This one, main, is especially detailed. Don’t worry, normally only one main method is expected and it is written this way by design. Let’s analyze it:

public: like classes, methods also use access modifiers. The main method is always public.
static: We have not learned about instance creation, but this means that this method can be used from other classes without creating instances of this class. The main method is always static.
void: the return type of the method. This method returns nothing, so it is set to void.
main: the name of the method. For main, the Java compiler will always expect it to be called that way.
(String[] args): The arguments of the method. String[] means that it is an array (a collection) of strings and args is the name of the argument. This is also default for the main method. In a method of its own, we would use something else, or nothing, depending on what we need.

Excellent! Remember that this (slightly scary) way of writing code is just a design decision of the language creators, and the Java compiler wants to see it somewhere in the program. Normally, it will go in a class called Main.java, but it’s not mandatory.

Finally we can print our important message to the world! And we do it with this line: System.out.println(“Meow, world!”); But what does that mean?

Compared to other languages like JavaScript, where the function to print is console.log(), or Python, where it is print(); this may seem a bit intimidating. Fear not, this is how it was done and it’s not that terrible.

If we get rid of the System.out part, we get to println, which is actually the name of the print function in some programming languages. Now we can see System.out as the origin of println, the classes where this method we are using comes from.

Once we get past this first, not very friendly, encounter with Java, we will be free to explore a really powerful, popular, in-demand and useful programming language with which we can practice object-oriented programming, learn to organize our programs and do a lot of things!

As you can see from the above, the theory of Java or any programming language can seem very convoluted. In Ubiqum we minimize the theory and bet on practice, the only real way to learn.

If you are a beginner who wants to learn to code or you have some coding knowledge in other languages and want to learn Java, you can come to Ubiqum Code Academy and take the Full Stack web development program with Java (online or on campus). and become a fluent programmer in this in-demand language.