Java Building Blocks: Java Classes Updated 2023

Classes are the most basic building blocks in Java. A class is like a blueprint of an object that you want to use over and over again. Below is the simplest form of a Java class.

public class Car {}

This is just a class, and it does nothing.

A class has two primary elements: methods and fields. A method is simply a function inside a Java class. A field is just a variable, interchangeably, you can use any of the other, but for Java's sake, we will call these how they are called expectedly in the Java exam.

Sample of a method:

public String getColor() { return color }

In the above sample method, the method name is getColor. Inside the getColor method is a field being returned named color. We want to make sense of the above snippet so we'll fit this inside the Car class.

public class Car {
    String color;
    public String color() {
        return color;
    }
}

Now this is a class that has a method(getColor) and a field(color) in it.

Let's leave this concept here and we'll get back here after we tackle the Java main method.

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Java main() Method

The java main method is the main entrypoint of any Java app. When we run a java file, the method that it bootstraps is the main method and it commonly looks like the one below:

public static void main(String[] args) {}

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Piecing it together...

We have this Car class.

public class Car {
    String color;
    public String getColor() {
        return color;
    }
}

And we have the main method

public static void main(String[] args) {}

Challenge: We want to give a value to the color field of the Car class and print it inside the main method. (You can refrain from checking the next code box as I will provide an answer in it But feel free to do so if you wanna checkout right away how this one will look like, no pressure.)

public class Car {
    String color;
    public String getColor() {
        return color;
    }
}
public static void main(String[] args) {
    Car myCar = new Car();
    myCar.color = "pink";
    System,out.println("My car color: " + myCar.getColor);
}

Save this as Car.java

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Let me skip the formalities on how to run a java program with a "Hello World" string. It's nice to deviate from the mainstream at times. Just follow the steps below to run your java program.

1. Open a command line and browse to the directory where you saved Car.java.

2. Type: javac Car.java then hit enter to compile your code.

3. Now, type ' java Car ' to run your program.

If you are encountering an error when trying to run any steps in the above instructions, more specifically this error: "not recognized as an internal or external command"*, you can read my other article on [how to install Java](misscharm.hashnode.dev/java-install-jdk-17-..) on your machine.*

The output of the program should print the following:

My car color: pink