Question

In Main:

Equipe Eq1 = new Equipe(J,E);
Equipe Eq2 = new Equipe(J,E);
while(Eq1.equals(Eq2))
Eq2 = new Equipe(J,E);

Match m = new Match(Eq1,Eq2);
String ChercherJoueur = m.QuelEquipe(m.hasBall());

In Class Equipe:

public Vector<Joueur> VJ;
public Equipe(Vector<Joueur> E, Vector<Entraineur> Ent) {
   VJ = new Vector<Joueur>();
   //rest of the logic
}
public Equipe() {
}

In Class Match:

Equipe Eq1 = new Equipe();
Equipe Eq2 = new Equipe();
public Match(Equipe Eq1, Equipe Eq2) {
Eq1 = this.Eq1;
Eq2 = this.Eq2;
}

public String QuelEquipe(Joueur J)
{
    boolean found = Eq1.ChercherJoueur(J);
    if(found == true)
        return "EQ1";
    else
        return "EQ2";
}

public Joueur hasBall()
{
    Joueur J = null;
    int i = 0;
    boolean found = false;

NullPointerException------->  System.out.println(Eq1.VJ.get(i).isBall());

System.out.println(Eq2.VJ.get(i).isBall());
    while(!found)
    {

        if((Eq1.VJ.get(i).isBall())==true)
        {
            found = true;
            J= Eq1.VJ.get(i);
        }

        else if((Eq2.VJ.get(i).isBall())==true)
        {
            found = true;
            J= Eq2.VJ.get(i);
        }
        i++;
    }
return J;
}
}

I think is all I need to include here to inform u about the situation.. I get a NullPointerException when I do “m.QuelEquipe(m.hasBall());” that can be traced back to where I pointed in The Class Match.. I know exactly what the exception means, and I’m changing their references with “Eq1 = this.Eq1;Eq2 = this.Eq2;” anyway.. sooo where is flow to get the code to work??

Answer 1

Your constructor using two args does initialize the vector but the parameterless constructor doesn’t

public Equipe(Vector<Joueur> E, Vector<Entraineur> Ent) {
    VJ = new Vector<Joueur>(); //<-- OK
    //rest of the logic
}
public Equipe() {
        //<-- errrk
}

Then when you invoke:

System.out.println(Eq2.VJ.get(i).isBall());

You’re using really invoking:

Eq2.null.get  <-- NullPointerException 

But the real problem though is in the Match constructor:

public Match(Equipe Eq1, Equipe Eq2) {
    Eq1 = this.Eq1;
    Eq2 = this.Eq2;
}

Here you’re assigning to the local variable Eq1 the value of the instance variable Eq1 you really want it the other way around:

public Match(Equipe Eq1, Equipe Eq2) {
    this.Eq1 = Eq1;
    this.Eq2 = Eq2;
}

BTW, this is not C# and in Java as a coding conventions both, methods and attributes start with lowecase and opening brace goes in the same line ( although this last part is not as relevant as the naming convention )

I hope this helps.