Introduction
Hello everyone! Since the last post served as a general introduction to Java, today we will be learning about the actual syntax of the language. Syntax is a set of rules that must be followed regarding the structure and format of the language. Before reading this article, I recommend downloading Eclipse by following the instructions online. I believe that it’s best to learn by doing, so follow along with me as I create a project!
Navigating Eclipse
Now that you have Eclipse open, press File on the top left of your screen-> New-> Java Project.
Name your project anything you want. Next, press the downwards arrow next to the project, and you’ll see “JRE System Library” and “src”. Right click on src -> New -> Package. Again, you can choose what to name your package.
Right click on your package -> New -> Class.
The first letter of the class should be in uppercase. Although lowercase is allowed, it’s discouraged. When you’re naming the class, make sure to check off the option that I have checked off.
And you’ve successfully set up your first project!
Structure
This is the basic overview of the structure of Java, but today we’ll only be focusing on classes and methods.
- Class: Every Java program starts with declaring a class. A class is a blueprint for an object, which all share common properties and methods within the class.
- Object: An object is an instance of a class, and has states and behavior.
- Methods: Methods are within a class and are used to perform a task.
- Instance variables: The values within the variables are used to describe the object. Each object has its own variables.
Unpacking the Code
I have written an additional line of code, but otherwise you should see the same code on your screen (I encourage you to add this code to your program, however). Let’s break down the code. Every Java program begins with declaring a class, and the main method is where the program starts executing.
As you can see, classes (Hello_World) and methods (main) have curly braces next to them. Although indentation is not required in Java, it helps me keep track of where my braces are. Curly braces are used to group statements together, and define the start and end of classes and methods. We know that System.out.println is the only line in the main method because there are closed braces after it.
System.out.println(value) prints the value and moves the cursor to the next line after that. This means that the next line that’s written after “Hello World” will be on the line below it. On the other hand, System.out.print() prints the value and waits at the end of the line. The next value that’s printed will be on the same line.
You may notice the semicolons after the System.out.println line. This is because each line of code inside the method must end with a semicolon, which is used to terminate a statement.
Conclusion
I hope that you followed along with my steps and were able to create your first program. First, we learned how to create a project in Eclipse. Next, we learned about the basic structure of Java with classes, objects, methods, and instance variables. Finally, we took a look at example code to see how braces and semicolons are used in Java, as well as how values are printed to the console.
