ArrayList returns null

[aborgeld]

I want to use this method for filling my combobox, i want to store information in an Arraylist, but this returns null, wheni print the method:

public ArrayList getPlaygroundStringList(Spel spelActief){
                    
        ArrayList <String> playgroundStringList = new ArrayList();
        
        for (int i = 0; i < spelActief.getPlaygroundAantal();i++)
            playgroundStringList.add(spelActief.playground.getNaam());
        
        return  this.playgroundStringList;
    }

1. The parameter works
2. when i print this (spelActief.playground.getNaam()) i get:
playground1

The purpose is to fill this arraylist when passing a playground.
playground1, playground2 and so on.

Why does it return null?

Kind regards,

André

[Petr]

It's easy. You have two variables. There are have the same name and you pass variable, which you are not fulling. Just delete key work "this" from there

return  [B]this[/B].playgroundStringList;

[aborgeld]

Thanks, your right, it works.
The for loop gives me.

I made another mistake to add the for loop there.
result:
playground1, playground1, playground1, playground1

So i've changed that. So the result is:

playground1

And when i start in level two the result is:
playground2

It seems like the first value is gone.

How do i get it to save every value that the getMethod gives?

like this: playground1, playground2 etc..

[aborgeld]

The new keyword makes a new instance in the method. Thats why.

[Petr]

Sorry It's difficult to understand for me. You can use forEach loop for it.
What is "spelActief.getPlaygroundAantal()" there?

[aborgeld]

Not a problem.

That gives me the active playground.

So if i play in playground 1 it gives playground1, when i get to the next playground, it gives me playgroud2.

And i want to store everything it gives me after i played each playground in an ArrayList.

[aborgeld]

This is what i want (see code), i managed to do it now, but the code is not so flexibel.
spelActief.playground.getName()), gives me the playground i'm on at the moment, example: playground1.
spelActief.getPlaygroundAantal(); gives me the sixe of the playgroundList.

public String[] getPlayground(Spel spelActief){

         String[] playGr1 = {"Playground 1"};
         String[] playGr2 = {"Playground 1", "Playground 2"};
         String[] playGr3 = {"Playground 1", "Playground 2", "Playground 3"};
         String[] playGr4 = {"Playground 1", "Playground 2", "Playground 3", "Playground 4"};

         if (spelActief.playground.getNaam().equals("playground1"))
            return playGr1;
         else if(spelActief.playground.getNaam().equals("playground2"))
            return playGr2;
         else if(spelActief.playground.getNaam().equals("playground3"))
            return playGr3;
         else
            return playGr4;
    }

playgroundComboBox = new JComboBox(spelHandler.getPlayground(spelActief));