Boletim (Getters & Setters) e Construtor

public class Boletim {
    private Decimal n1;
    private Decimal n2;
    private Decimal n3;
    private Decimal n4;
    private Decimal media;

    public Boletim(){

    }
    public Boletim(Decimal n1, Decimal n2, Decimal n3, Decimal n4){
        this.n1 = n1;
        this.n2 = n2;
        this.n3 = n3;
        this.n4 = n4;

    }
    public void setN1(Decimal n1){
        this.n1 = n1;
    }
    public void setN2(Decimal n2){
        this.n2 = n2;
    }
    public void setN3(Decimal n3){
        this.n3 = n3;
    }
    public void setN4(Decimal n4){
        this.n4 = n4;
    }
    public Decimal getMedia(){
        return this.media;
    }
    public String calculaMedia(){
        this.media = (n1+n2+n3+n4)/4;
        if(this.media>=5){
            if(this.media>10){
                return 'Nota incorreta';
            }
            return 'Aprovado';
        }else if(media>=4){
            return 'Recuperação';
        }else{
            return 'Reprovado';
        }
    }
}

//ANONYMOUS
/*Boletim b = new Boletim();
b.setN1(5);
b.setN2(8);
b.setN3(3);
b.setN4(10);
System.debug(b.calculaMedia()+' - '+b.getMedia());*/

/*Boletim b = new Boletim(5, 8, 3, 10);
System.debug(b.calculaMedia()+' - '+b.getMedia());*/