Using generics to restrict object initialisation and commparable interface to sort.

SportsTeams.java

import java.util.ArrayList;
import java.util.Collections;

public class Udemy {


    public static void main(String[] args) {
        League<FootballTeam> premierLeague = new League<>("Premier League");
        FootballTeam tottenham = new FootballTeam("Tottenham Hotspur",38,0, 0);
        FootballTeam arsenal = new FootballTeam("Arsenal", 0,0, 38);
        FootballTeam bournemouth = new FootballTeam("AFC Bournemouth", 23, 7, 8);

        premierLeague.addTeam(tottenham);
        premierLeague.addTeam(arsenal);
        premierLeague.addTeam(bournemouth);

        premierLeague.printLeagueTable();
        
        /* 
        Premier League
        Tottenham Hotspur W:38 D:0 L:0 Points: 114
        AFC Bournemouth W:23 D:7 L:8 Points: 76
        Arsenal W:0 D:0 L:38 Points: 0 
        */
        
        System.out.println(premierLeague.toString());
        
        /* 
        Tottenham Hotspur
        AFC Bournemouth
        Arsenal 
        */

        League<CricketTeam> indianPremierLeague = new League<>("Indian Premier League");
        CricketTeam chennai = new CricketTeam("Chennai Super Kings", 10, 0, 0);
        CricketTeam delhi = new CricketTeam("Delhi Capitals", 9, 1, 0);
        CricketTeam kings = new CricketTeam("Kings XI Punjab", 7, 2, 1);

        indianPremierLeague.addTeam(chennai);
        indianPremierLeague.addTeam(delhi);
        indianPremierLeague.addTeam(kings);

        /* Compile time error, type is not a CricketTeam. Prevents teams being added to the wrong league
         using generic classes and type bounds */

//        indianPremierLeague.addTeam(bournemouth);

        indianPremierLeague.printLeagueTable();
        
        /* 
        Indian Premier League
        Chennai Super Kings W:10 D:0 L:0 Points: 30
        Delhi Capitals W:9 D:0 L:1 Points: 27
        Kings XI Punjab W:7 D:1 L:2 Points: 22 
        */

    }


}

/* Generic class that accepts types of SportsTeam and subclasses of SportsTeam. Upper type bounded */
class League<T extends SportsTeam>  {

    private String leagueName;
    /* ArrayList only accepts class type T. These will be objects of SportsTeam and subclasses */
    public ArrayList<T> teams = new ArrayList<>();


    public League(String leagueName) {
        this.leagueName = leagueName;
    }

    public void addTeam(T team) {
        teams.add(team);
    }

    public void printLeagueTable() {
        Collections.sort(teams);
        System.out.println(leagueName);
        for (T team : teams) {
            System.out.println(team.toString());
        }
    }

    @Override
    public String toString() {
        StringBuilder teamName = new StringBuilder();
        for (T team : teams) {
            teamName.append(team.getName()).append("\n");
        }
        return teamName.toString();
    }
}

class SportsTeam implements Comparable<SportsTeam> {

    private String name;
    private int wins;
    private int draws;
    private int losses;

    @Override
    public String toString() {
        return name + " W:" + wins + " D:" + draws + " L:" + losses + " Points: " + getRanking();
    }

    public SportsTeam(String name, int wins, int draws, int losses) {
        this.name = name;
        this.wins = wins;
        this.draws = draws;
        this.losses = losses;
    }

    public int getRanking() {
        return wins * 3 + draws;
    }

    public String getName() {
        return name;
    }

    /* This method will be used with Collections.sort() to order the collection of SportsTeam objects */
    @Override
    public int compareTo(SportsTeam otherTeam) {
        if (this.getRanking() > otherTeam.getRanking()) {
            return -1;
        } else if (this.getRanking() == otherTeam.getRanking()) {
            return 0;
        } else {
            return 1;
        }
    }
}

class FootballTeam extends SportsTeam {
    public FootballTeam(String name, int wins, int draws, int losses) {
        super(name, wins, draws, losses);
    }
}

class RugbyTeam extends SportsTeam {
    public RugbyTeam(String name, int wins, int draws, int losses) {
        super(name, wins, losses, draws);
    }
}

class CricketTeam extends SportsTeam {
    public CricketTeam(String name, int wins, int draws, int losses) {
        super(name, wins, losses, draws);
    }
}