Question

So basically I have this constructor for the class League:

import java.util.*;

public class League {

    private String name;
    private List<Team> teamList;

    public League(String name) {        
        List<String> teamNames = new LinkedList<String>(Company.teamList);
        Collections.shuffle(teamNames);
        teamNames.subList(0, 5);

        for(int i = 0; i < teamNames.size(); i++){
            teamList.add(new Team(teamNames.get(i)));
        }
}
}

The class Company happens to have a Set called teamList.
When I call on System.out.println(teamNames.get(i)) it shows me the content so obviously the elements of the set are there, however when I try to create a new Team object based on the elements of the list of Strings, it gives me a NullPointerException. I don’t know why is that? Help?

Here is the code for the Team class in case you need it:

import java.util.HashMap;
import java.util.Map;


public class Team {

    protected Map<Integer, Player> teamPlayerMap;
    private String teamName;

    public Team(String name) {
        teamPlayerMap = new HashMap<Integer, Player>();
        teamName = name;
    }

    public String getTeamName() {
        return teamName;
    }


}

Answer 1

I think the problem is here:

private List<Team> teamList;

public League(String name) {        
    // etc...

    for(int i = 0; i < teamNames.size(); i++) {
        teamList.add(new Team(teamNames.get(i))); // This will throw!
    }
}

You need to create an instance of a class that implements List<Team> and assign it to teamList. You haven’t done this so it will throw a NullPointerException when you call teamList.add(...).

The fix is to write this instead:

private List<Team> teamList = new ArrayList<Team>();