Inherit problems

Question

Dear reader,
I have a problem. In my first class I have a collection and I need to inherit all it is value's to another class. My code:
{color:#339966}public class Hattrick extends JPanel implements ActionListener {
…
Collection<Speler> spelers = new ArrayList<Speler>();
public Collection<Speler> getCollection() {
return this.spelers;
&hellip;
{color}
And here is the class where the collection needs to be inherit:
{color:#339966}public class ToolActies extends AbstractAction {
protected Hattrick hattrick;
{color}
{color:#339966}public void actionPerformed(ActionEvent e) {
Collection<Speler> spelers = hattrick.getCollection();
&hellip;
{color}
But Collection<Speler> spelers = hattrick.getCollection(); give exception
{color:#339966}Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at ToolActies.actionPerformed(ToolActies.java:30)
...{color}
Anybody has a clue how to inherit the collection? I owe you already
Greets,
Vinvar

Answer 1

This is composition, not inheritance, and you forgot to do something like this:
public class ToolActies extends AbstractAction {
    private Hattrick hattrick;
    public ToolActies(Hattrick hattrick) {
        this.hattrick = hattrick; //<<<------
}