Unknown NullPointerException in my program "Date"

Question

Well, I've been keeping practicing Java and after a while I decided to create a program that operates with Dates. My problem is that when I did a test of my class, I get a NullPointerException and I don't know where the error is. Here's my interface:

package fecha;

public interface Fecha extends Cloneable, Copiable<Fecha>, Comparable<Fecha> {

    Integer getDia();
    Integer getMes();
    Integer getAnnio();
    void setDia(Integer dia);
    void setMes(Integer mes);
    void setAnnio(Integer annio);
    Boolean esBisiesto();
    void fechaAnterior();
    void fechaSiguiente();
}

Here's the class:

package fecha;

import java.util.Objects;

public class FechaImpl implements Fecha{

    //Atributos

    private Integer dia;
    private Integer mes;
    private Integer annio;

    //Métodos get/set

    public Integer getDia(){

        return dia;
    }

    public Integer getMes(){

        return mes;
    }

    public Integer getAnnio(){

        return annio;
    }

    public void setDia(Integer d){

        if(d < 1 || d > 31){

            throw new IllegalArgumentException("Dia no valido");
        }

        Integer numeroDias = 30;

        switch(getMes() ){

            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                numeroDias = 31;
                break;
            case 2:
                numeroDias = esBisiesto() ? 29 : 28;
                break;
        }

        if (d > numeroDias) throw new IllegalArgumentException("Dia no valido");

        this.dia = d;
    }

    public void setMes(Integer m){

        if(m < 1 || m > 12){

            throw new IllegalArgumentException("Mes no valido");
        }

        this.mes = m;
    }

    public void setAnnio(Integer a){

        if(a < 1900){

            throw new IllegalArgumentException("Annio no valido");
        }

        this.annio = a;
    }
    //Métodos constructores

    public FechaImpl(Integer d, Integer m, Integer a){

        setDia(d);
        setMes(m);
        setAnnio(a);
    }

    public FechaImpl(String fecha){

        String[] dato = fecha.split("/");

        setDia(Integer.parseInt(dato[0]));
        setMes(Integer.parseInt(dato[1]));
        setAnnio(Integer.parseInt(dato[2]));
    }

    //Otros métodos

    public Boolean esBisiesto(){

        Boolean res;
        res = ((getAnnio() % 4 == 0) && ((getAnnio() % 100 != 0) || (getAnnio() % 400 == 0))) ? true : false;

        return res;
    }

    public void fechaAnterior(){
        if(getDia().compareTo(1) == 0){
            setDia(30);
            if(getMes().compareTo(1) == 0){
                setMes(12);
                setAnnio(getAnnio() - 1);
            }else {
                setMes(getMes() - 1);
            }
        }else {
            setDia(getDia() - 1);
        }   
    }

    public void fechaSiguiente(){
        if(getDia().compareTo(30) == 0){
            setDia(1);
            if(getMes().compareTo(12) == 0){
                setMes(1);
                setAnnio(getAnnio() + 1);
            }else {
                setMes(getMes() + 1);
            }
        }else {
            setDia(getDia() + 1);
        }

    }

    //Comparable

    public int compareTo(Fecha o){

        int res = getAnnio().compareTo(o.getAnnio());
        if(res == 0){
                res = getMes().compareTo(o.getMes());
                if(res == 0){
                    res = getDia().compareTo(o.getDia());
                }
        }
        return res;
    }

    //Equals/hashcode

    @Override

    public boolean equals(Object o){

        boolean res = false;
        if(o instanceof Fecha){

            Fecha f = (Fecha) o;
            res = getDia().equals(f.getDia()) && getMes().equals(f.getMes()) && getAnnio().equals(f.getAnnio());
        }
        return res;
    }

    @Override

    public int hashCode(){

        return Objects.hash(this.getDia(), this.getMes(), this.getAnnio());
    }

    //A cadena

    @Override

    public String toString(){

        String s = "[" + getDia() + "," + getMes() + "," + getAnnio() + "]";
        return s;
    }

    //Cloneable

    @Override

    public Fecha clone(){

        Fecha copia = null;
        try{
            copia = (Fecha) super.clone();
        } catch (CloneNotSupportedException e){

            e.printStackTrace();
        }

        return copia;
    }
}

And here's the test (main):

package fecha;

public class Main {

    public static void main(String[] args) {

        FechaImpl prueba = new FechaImpl ("20/10/1995");
        FechaImpl test = new FechaImpl (20, 10, 1995);

        System.out.println(prueba);
        System.out.println(test);

    }

}

I suspect that the problem exits in the switch case from method setDia() (lane 39), but I've been trying to change it and nothing happens.

EDIT: Yes you were right guys! The error was so simple as changing the setters in my constructor method. Here's the fixed class if you want to use it. Thank you a lot!

//Atributos

private Integer dia;
private Integer mes;
private Integer annio;

//Métodos get/set

public Integer getDia(){

    return dia;
}

public Integer getMes(){

    return mes;
}

public Integer getAnnio(){

    return annio;
}

public void setDia(Integer d){

    if(d < 1 || d > 31){

        throw new IllegalArgumentException("Dia no valido");
    }

    Integer numeroDias = 30;

    switch(getMes() ){

        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            numeroDias = 31;
            break;
        case 2:
            numeroDias = esBisiesto() ? 29 : 28;
            break;
    }

    if (d > numeroDias) throw new IllegalArgumentException("Dia no valido");

    this.dia = d;
}

public void setMes(Integer m){

    if(m < 1 || m > 12){

        throw new IllegalArgumentException("Mes no valido");
    }

    this.mes = m;
}

public void setAnnio(Integer a){

    if(a < 1900){

        throw new IllegalArgumentException("Annio no valido");
    }

    this.annio = a;
}
//Métodos constructores

public FechaImpl(Integer d, Integer m, Integer a){

    setAnnio(a);
    setMes(m);
    setDia(d);
}

public FechaImpl(String fecha){

    String[] dato = fecha.split("/");

    setAnnio(Integer.parseInt(dato[2]));
    setMes(Integer.parseInt(dato[1]));
    setDia(Integer.parseInt(dato[0]));
}

//Otros métodos

public Boolean esBisiesto(){

    Boolean res;
    res = ((getAnnio() % 4 == 0) && ((getAnnio() % 100 != 0) || (getAnnio() % 400 == 0))) ? true : false;

    return res;
}

public void fechaAnterior(){
    if(getDia().compareTo(1) == 0){
        setDia(30);
        if(getMes().compareTo(1) == 0){
            setMes(12);
            setAnnio(getAnnio() - 1);
        }else {
            setMes(getMes() - 1);
        }
    }else {
        setDia(getDia() - 1);
    }   
}

public void fechaSiguiente(){
    if(getDia().compareTo(30) == 0){
        setDia(1);
        if(getMes().compareTo(12) == 0){
            setMes(1);
            setAnnio(getAnnio() + 1);
        }else {
            setMes(getMes() + 1);
        }
    }else {
        setDia(getDia() + 1);
    }

}

//Comparable

public int compareTo(Fecha o){

    int res = getAnnio().compareTo(o.getAnnio());
    if(res == 0){
            res = getMes().compareTo(o.getMes());
            if(res == 0){
                res = getDia().compareTo(o.getDia());
            }
    }
    return res;
}

//Equals/hashcode

@Override

public boolean equals(Object o){

    boolean res = false;
    if(o instanceof Fecha){

        Fecha f = (Fecha) o;
        res = getDia().equals(f.getDia()) && getMes().equals(f.getMes()) && getAnnio().equals(f.getAnnio());
    }
    return res;
}

@Override

public int hashCode(){

    return Objects.hash(this.getDia(), this.getMes(), this.getAnnio());
}

//A cadena

@Override

public String toString(){

    String s = "[" + getDia() + "," + getMes() + "," + getAnnio() + "]";
    return s;
}

//Cloneable

@Override

public Fecha clone(){

    Fecha copia = null;
    try{
        copia = (Fecha) super.clone();
    } catch (CloneNotSupportedException e){

        e.printStackTrace();
    }

    return copia;
}

Possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — xlecoustillier, Oct 06 '15 at 11:43
"I don't know where the error is" - did you check the exception stack trace to see where it is? — daiscog, Oct 06 '15 at 11:51

score 1 · Accepted Answer · answered Oct 06 '15 at 11:45

1

You haven't set your mes attribute which is used in setter of dia attribute

answered Oct 06 '15 at 11:45

dpassy

363
1
10

correct ... `setDia` uses `mes` attribut .... `setMes` should be called before setDia ... +1 – Pras Oct 06 '15 at 11:49
You're completely right, the error was so simple as that. Thank you a lot! – xFunkyTImes Oct 06 '15 at 11:50

score 0 · Answer 2 · answered Oct 06 '15 at 11:49

Change order of setters in your constructor:

        public FechaImpl(Integer d, Integer m, Integer a){
            setMes(m);
            setDia(d);
            setAnnio(a);
        }

        public FechaImpl(String fecha){

            String[] dato = fecha.split("/");

            setMes(Integer.parseInt(dato[1]));
            setDia(Integer.parseInt(dato[0]));
            setAnnio(Integer.parseInt(dato[2]));
        }

You must set month first, because you are using it inside setting day.

score 0 · Answer 3 · answered Oct 06 '15 at 11:50

You are depending on things already being set.

setDia calls getMes()
setDia also calls esBisiesto() which calls getAnnio()

But both Annio and Mes are not initialized yet.

An easy way to fix it is to reorder the constructor:

    setAnnio(a);
    setMes(m);
    setDia(d);

Unknown NullPointerException in my program "Date"

3 Answers3