A combination of Procedural and Object-oriented

The first lesson I’ve learned about Java is what its programming styles are. The first one is a very common one, which is Procedural. Think of traditional constructs such as functions, conditionals, loops and so on. You might wonder; does not every programming language has this? If I mention a couple of declarative languages you’ll immediately realize. Think of HTML, CSS, or SQL.

public class ProceduralExample {
    static int countCompletedLessons(boolean[] lessons) {
        int completed = 0;

        for (boolean lessonCompleted : lessons) {
            if (lessonCompleted) {
                completed++;
            }
        }

        return completed;
    }

    public static void main(String[] args) {
        boolean[] lessons = {true, true, false, true};
        int completed = countCompletedLessons(lessons);

        System.out.println("Completed lessons: " + completed);
    }
}

Then the other programming style used by Java is the Object-oriented one. When you talk about this you’ll rapidly run into Objects (duh!), classes, inheritance, polymorphism, etc. If you have a front-end background you might have been less in contact with these lately, but they are still present in the world of JavaScript.

public class CourseProgress {
    private final int totalLessons;
    private int completedLessons;

    public CourseProgress(int totalLessons) {
        this.totalLessons = totalLessons;
    }

    public void completeLesson() {
        if (completedLessons < totalLessons) {
            completedLessons++;
        }
    }

    public void printProgress() {
        System.out.println(
            "Completed lessons: " + completedLessons + "/" + totalLessons
        );
    }
}