CODEWITHSUNDEEP
javaalgorithmdata-structureshashmap
unleashed
unleashed

Reputation: 925

Implementing a custom Data Structure to replace 2 hashmaps

I'm using two ConcurrentHashMaps to store the following data. I'll use the following as an example

private Map<Player, FootballTeam> playerTeamMapping;
private Map<FootballTeam, League> teamLeagueMapping;

Given just the FootballTeam object, I need to be able to retrieve either the Player or League objects and perform some operations

Cases to consider:

So far i'm using both maps defined above but for learning purposes, i've been told I will need to define my own data structure to solve this problem.

I'm thinking of creating of creating a generic class ThreeWayHashMap<Left, Middle, Right> that is backed by the 2 maps (Left = Player, Middle = FootballTeam, Right = League). Is this the best approach to take? I need to basically keep three maps in sync when deleting so when removing entries (i'll need to make sure I perform these operations on both).

Upvotes: 1

Views: 153

Answers (1)

RP-
RP-

Reputation: 5837

You can use your existing classes to represent the mapping. League should have Set<FootballTeam> and FootballTeam should have Set<Player> and both League and FootballTeam should have utility methods to add or remove a player from the team and add or remove a team from league.

public class League {
    Set<FootballTeam> teams = new HashSet<FootballTeam>();

    public void addPlayer(FootballTeam team, Player player) {
        team.addPlayer(player);
        teams.add(team);
    }

    public void removePlayer(FootballTeam team, Player player) {
        team.removePlayer(player);
        teams.remove(team);
    }

    public void movePlayer(FootballTeam from, FootballTeam to, Player player) {
        from.movePlayerTo(to, player);
        if (from.getPlayers().size() == 0 ) {
            teams.remove(from);
        }
        teams.add(to);
    }
}

public class FootballTeam {
    private Set<Player> players = new HashSet<Player>();

    public void addPlayer(Player player) {
       player.setTeam(this);
       players.add(player);
    }

    public void removePlayer(Player player) {
       player.setTeam(null);
       players.remove(player);
    }

    public void movePlayerTo(FootballTeam to, Player p) {
       player.setTeam(to);
       players.remove(p);
    }
}

Upvotes: 1

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