在Java中，一对多关系是指一个对象可以关联多个其他对象。

示例代码如下：

// 一的一方  
class Team {  
    private String name;  
    private List<Player> players;  
    public Team(String name) {  
        this.name = name;  
        this.players = new ArrayList<>();  
    }  
    public void addPlayer(Player player) {  
        players.add(player);  
    }  
    public void removePlayer(Player player) {  
        players.remove(player);  
    }  
}  
// 多的一方  
class Player {  
    private String name;  
    private Team team;  
    public Player(String name) {  
        this.name = name;  
    }  
    public void setTeam(Team team) {  
        this.team = team;  
    }  
}  
// 测试程序  
public class Main {  
    public static void main(String[] args) {  
        Team team = new Team("Team A");  
        Player player1 = new Player("Player 1");  
        Player player2 = new Player("Player 2");  
        Player player3 = new Player("Player 3");  
        team.addPlayer(player1);  
        team.addPlayer(player2);  
        team.addPlayer(player3);  
        System.out.println("Team: " + team.getName());  
        System.out.println("Players: " + team.getPlayers());  
        team.removePlayer(player2);  
        System.out.println("Updated Players: " + team.getPlayers());  
        player3.setTeam(team);  
        System.out.println("Updated Team for Player 3: " + player3.getTeam().getName());  
    }  
}  

在上面的示例中，Team代表一的一方，Player代表多的一方。Team类包含一个List<Player>来存储与该团队相关联的球员。Player类包含一个Team对象来表示球员所属的团队。

在测试程序中，我们创建一个团队对象并添加三个球员对象。我们还演示了如何删除一个球员，并将另一个球员与团队建立关联。