Cannot add to arraylist inside while loop inside the main method

Question

I made a program that utilizes 3 classes, Championship, Game and Club. My methods inside game and club are fine but it's in the main method of Championship class where I'm having issues. I have 2 arraylists, one with objects club and one with objects game. In my main method, I created a menu using a while loop and switch case for the user to 1- create a club, 2- create a game, 3- list results, and 4- register results. However, all my cases have the same issue: the non static variables (arraylists) cannot be accessed in the static context. So, I don't know how to access my arraylists. Everywhere I get an error, there's a comment, but again, they are all the same and all regard the arraylists. Help's appreciated!

Leaving relevant code down here with comments on where Im getting this error.

public class Championship{


    ArrayList<Club> clubs;
    ArrayList<Game> games;

    public Championship() {
        clubs = new ArrayList();
        games = new ArrayList();
    }
    
    
    
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int option = -1;
        
        while(option!=0){
            System.out.println("\t1- Create Club");
            System.out.println("\t2- Create game");
            System.out.println("\t3- List results");
            System.out.println("\t4- Register result by index");
            option = sc.nextInt();
            switch( opçao ){
                case 1:
                    System.out.println("Insert club name.");
                    String n = sc.nextLine();
                    sc.nextLine();
                    System.out.println("Insert club city.");
                    String c = sc.nextLine();
                    sc.nextLine();
                    clubs.add(new Club(n, c)); //ERROR: non static clubs cannot be referenced here in static context
                    break;
                case 2:
                    Iterator<Club> iter = clubs.iterator(); //ERROR: non static clubs cannot be referenced here in static context
                    while(iter.hasNext()){
                        Club a = iter.next();
                        Club b = iter.next();
                        if(a != b){
                           games.add(new Game(a, b)); //ERROR: non static games cannot be referenced here in static context
                        }
                    }
                    break;
                case 3:
                    for(Game game : games){  //ERROR: non static clubs cannot be referenced here in static context
                        System.out.println(game.getM() + " : " + game.getN());
                    }
                case 4:
                    System.out.println("Game index");
                    int s = sc.nextInt();
                    sc.nextInt();
                    System.out.println("Goals visited?");
                    int N = sc.nextInt();
                    sc.nextInt();
                    System.out.println("Goals Visitor?");
                    int M = sc.nextInt();
                    sc.nextInt();
                    
                    Iterator<Game> iter2 = games.iterator(); //ERROR: non static clubs cannot be referenced here in static context
                    while(iter2.hasNext()){
                        Game j = games.get(s); //ERROR: non static clubs cannot be referenced here in static context
                        j.setResult(N,M);
                        
                }
                    break;
            }
        }

public class Club {
    private String name;
    private String city;

    public Clube(String name, String city) {
        this.name = name;
        this.city = city;
    }

    public String getCity() {
        return city;
    }

    public String getName() {
        return name;
    }
}

public class Game{
    private Clube visited;
    private Clube visitor;
    private int N;
    private int M;

    public Game(Club visited, Club visitor) {
        this.visited= visited;
        this.visitor= visitor;
    }


    public void setResult(int N, int M) {
        this.N = N;
        this.M = M;
    }

    public int getM() {
        return M;
    }

    public int getN() {
        return N;
    }

Here's a link on why you cant access non-static variables from a static context. https://stackoverflow.com/q/2559527/16034206 — experiment unit 1998X, Jul 03 '22 at 16:19
simply put, in your case you can move all the code from your main method in to a second helper method, and initialize the Championship object in your main method ```Championship c = new Championship();``` and call the helper method. ```c.helperMethod();``` — experiment unit 1998X, Jul 03 '22 at 16:24

score -1 · Answer 1 · answered Jul 03 '22 at 16:38

fix from @experiment unit 1998X

     public void Run(){
        Scanner sc = new Scanner(System.in);
        int option = -1;
        
        while(option!=0){
            System.out.println("\t1- Create Club");
            System.out.println("\t2- Create game");
            System.out.println("\t3- List results");
            System.out.println("\t4- Register result by index");
            option = sc.nextInt();
            switch( opçao ){
                case 1:
                    System.out.println("Insert club name.");
                    String n = sc.nextLine();
                    sc.nextLine();
                    System.out.println("Insert club city.");
                    String c = sc.nextLine();
                    sc.nextLine();
                    clubs.add(new Club(n, c)); 
                    break;
                case 2:
                    Iterator<Club> iter = clubs.iterator(); 
                    while(iter.hasNext()){
                        Club a = iter.next();
                        Club b = iter.next();
                        if(a != b){
                           games.add(new Game(a, b)); 
                        }
                    }
                    break;
                case 3:
                    for(Game game : games){  
                        System.out.println(game.getM() + " : " + game.getN());
                    }
                case 4:
                    System.out.println("Game index");
                    int s = sc.nextInt();
                    sc.nextInt();
                    System.out.println("Goals visited?");
                    int N = sc.nextInt();
                    sc.nextInt();
                    System.out.println("Goals Visitor?");
                    int M = sc.nextInt();
                    sc.nextInt();
                    
                    Iterator<Game> iter2 = games.iterator();                     
                      while(iter2.hasNext()){
                        Game j = games.get(s); 
                        j.setResult(N,M);
                        
                }
                    break;
            }
     }
}


public static void main(String[] args) {
    Championship c = new Championship();
    c.Run();
        }

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Cannot add to arraylist inside while loop inside the main method

1 Answers1