I'm currently working on a knock-out tournament

Overall Requirements:
-UserInput for 8 teams (teamName and playerNames) stored in a file (MY test is currently with 2 teams)
-Setup for matches (who vs. who) stored in a file
-Results of the matches with points to the team(s) stored in a file
-Ranking so we know who is out/in of the tournament

*****CURRENT PROBLEM IS THIS*******
I need a method which takes a team from my ArrayList<Team> or file (teamData.txt) and put it against another team - BOTH chosen from the user
e.g. with 8 teams (team1-team8)
team1 vs. team5

Afterwards saves the match data in a file

I HAVE NO CLUE ON HOW MY APPROACH SHOULD BE IN THIS... Any inputs? Thanks in advance


public class Main {
    public static void main(String[] args) {
 
            Tournament tournament = IO.input(2);
            IO.writeTeamFile(tournament);
            FileIO.readGameData();
    }
}
import java.util.ArrayList;
 
public class Tournament {
 
    private ArrayList<Team> teams;
 
    public Tournament() {
        this.teams = new ArrayList<Team>();
    }
    public ArrayList<Team> getTeams() {
        return teams;
    }
}
import java.util.ArrayList;
 
public class Team {
 
    private String name;
    private ArrayList<Player> players;
 
    public Team(String name) {
        this.name = name;
        this.players = new ArrayList<Player>();
    }
 
    public String getName() {
        return name;
    }
 
    public ArrayList<Player> getPlayers() {
        return players;
    }
}

public class Player {
 
    private String name;
 
    public Player(String name) {
        this.name = name;
    }
 
    public String getName() {
        return name;
    }
}
import java.io.FileWriter;
import java.util.Scanner;
 
public class IO {
    private static Scanner scan = new Scanner(System.in);
    public static int teamCount;
 
    private static String readUserInput(String msg) {
        System.out.print(msg);
        return scan.nextLine();
    }
 
    public static Tournament input(int numTeams) {
        Tournament tournament = new Tournament();
        for (int i = 0; i < numTeams; i++) {
            String teamName = readUserInput("Team name: ");
            Team team = new Team(teamName);
            tournament.getTeams().add(team);
 
            int numPlayersPerTeam = Integer.parseInt(readUserInput("Hvor mange spillere er der på holdet?"));
 
            for (int j = 0; j < numPlayersPerTeam; j++) {
                String playerName = readUserInput("Player name: ");
                Player player = new Player(playerName);
                team.getPlayers().add(player);
            }
        }
        return tournament;
    }
 
    public static void writeTeamFile(Tournament tournament) {
        try{
        FileWriter fileWriterDefault = new FileWriter("src/teamData.txt");
        fileWriterDefault.write("teamName, teamPlayers");
        fileWriterDefault.close();
        } catch (Exception e) {
            e.getStackTrace();
        }
 
        for (Team team : tournament.getTeams()) {
            String fullPlayerNames = "";
            teamCount ++; //Later use to numMatches
 
            for (Player player : team.getPlayers()) {
                String tmpPlayer = player.getName() + ", ";
                fullPlayerNames = fullPlayerNames + tmpPlayer;
            }
 
            try {
                FileWriter fileWriter = new FileWriter("src/teamData.txt", true);
                fileWriter.write("\n"+ team.getName() + ", " + fullPlayerNames);
                fileWriter.close();
            } catch (Exception e) {
                e.getStackTrace();
            }
        }
        System.out.println(teamCount);
    }
}

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
 
public class FileIO {
 
    public static void readGameData() {
 
            String path = "src/teamData.txt";
            String teamNamesFile = "";
 
            try{
                BufferedReader br = new BufferedReader(new FileReader(path));
                br.readLine(); //Reads first line, so it skips the header
                while((teamNamesFile = br.readLine()) != null){
                    String [] teamNames = teamNamesFile.split(",");
                    System.out.println("Team fra fil :" + teamNames[0]);
                }
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
    }
}

teamData.txt under here:
teamName, teamPlayers
teamA, A1, A2, A3, A4,
teamB, B1, B2, B3, B4


public class Match {
 
    public static void Match() {
 
 
    }
}