public class Gamermathijs extends AboutMe {

    public Gamermathijs() {
        super("Gamermathijs", "Netherlands");

        this.addTopLanguages("C#", "Java")
        this.addLanguage("html", "css", "javascript", "nodejs");
    }
}

public abstract class AboutMe {

    private final String name;
    private final String country;

    private ArrayList<String> topLanguages = new ArrayList<>();
    private ArrayList<String> languages = new ArrayList<>();
    
    public GitHubUser(String name, String country) {
        this.name = name;
        this.country = country;
    }

    public void addTopLanguages(String... topLanguages) {
        topLanguages.addAll(topLanguages);
    }
    
    public void addLanguage(String... language) {
        languages.addAll(language);
    }
}