在子类中初始化超类数组（java）

Question

I am new to JAVA / Android programming and have a small problem.

I created in a Superclass a Array and wanted to initialize it in multiple subclasses. But when I try to initialize it, it says it's not possible.

My code:

public abstract class Fragen {

 String[] Deutsch;
 String[] Slowakisch;

static int Anzahl;
Random random;
int randNumber;

byte Fächer;

public String displayQuestion()
{

    //TODO Fach abfragen
    randNumber = random.nextInt(Anzahl);

    return Slowakisch[randNumber];

}

public boolean correctAnswer(String answer)
{
    //TODO Fächer +/-

    if(answer.equals(Deutsch[randNumber]))
        return true;

    else
        return false;
}
}

(Superclass)

 public class Lektion1 extends Fragen
{
    private Lektion1()
    {
        super();
        Anzahl = 60;
        //Deutsch = new String[];
        Deutsch = {"",""};
        Slowakisch = {"",""};
    }
}

(Subclass)

Kind regards Thomas

Answer 1

Try this:

public class Lektion1 extends Fragen
{
    private Lektion1()
    {
        super();
        Anzahl = 60;
        //Deutsch = new String[];
        Deutsch = new String[]{"", ""};
        Slowakisch = new String[]{"", ""};
    }
}

Answer 2

Just create a constructor in your super class and initialize that array there:

public abstract class Fragen {
    ...
    public Fragen() {
        Deutsch = new String[];
    }
    ...
}

---

alternative

or if your fields have appropriate access modifiers, then you can also access them using super keyword

public abstract class Fragen {
    public String[] Deutsch;
    ...
    ...
}

and in base class:

public class Lektion1 extends Fragen {
    private Lektion1()
    {
        super();
        Anzahl = 60;
        super.Deutsch = new String[];
        Deutsch = {"",""};
        Slowakisch = {"",""};
    }
}

Answer 3

Edit: For a conrete answer to your concrete question, @MrQuattro's answer is of course correct and fulfilling.

That said, if you want to learn more of object-oriented design, I still myself like the ideas from my original answer. You can of course throw away or use as you see fit: I propose that it will be more convenient to keep the German and the Slovakian word together, so I'd make a class Frage to hold one word (or phrase or expression) in both languages.

Next I'd want to make a constructor in Fragen that accepts all the Frage objects, for instance as varargs (you should learn about those). This will allow the Lektion1 constructor to contain just

super(new Frage("", ""), new Frage("", ""), new Frage("", ""));

Fragen can count, so you don't need to: the superclass constructor will set anzahl (please use lowercase a for a variable) to the number of questions received.

If you want to take it a step further, the Frage class could also be given the responsibility of checking whether an answer is correct.

Link: Anti-pattern: parallel collections