java - 控制台输入到 arraylist java 中，没有重复输入

Question

任务:编写一个 Java 程序，允许该程序的用户为 field 中 8 个跑道跑道的每一个跑道分配一名运行者。

我能够让输入进程、数组列表、setter 和 getter 正常工作，但我的问题是我很难理解如何将 8 个 channel 的输入数量限制为每个运行者只能分配一个 channel 。这是我当前输入的代码:

public List<Item> createListOfCompetitors(){

    List<Item> newListOfCompetitors = new ArrayList<>();

    try (Scanner sc = new Scanner(System.in)) {
        do {
            System.out.println("Enter Competing Runner Name");
            String name = sc.nextLine();

            System.out.println("Assign a lane to the runner! ");
            while (!sc.hasNextDouble()) {
                System.out.println("Use a valid number");
                sc.next();
            }
            double lane = sc.nextDouble();
            Item item = new Item(name, lane);
            newListOfCompetitors.add(item);
            System.out.println("Enter Y to continue or N to quit");
            sc.nextLine();
        } while (sc.nextLine().equalsIgnoreCase("y"));
    }
    return newListOfCompetitors;
}

Dependencies in my program

Answer 1

我可能会选择使用车道 map 来表示被占用的车道。这样，您可以添加一个条件来检查从控制台输入的车道是否已被占用。

public Map<Double, Item> createListOfCompetitors() {
    Map<Double, Item> lanes = new HashMap<>();

    try (Scanner sc = new Scanner(System.in)) {
        do {
            System.out.println("Enter Competing Runner Name");
            String name = sc.nextLine();

            System.out.println("Assign a lane to the runner! ");
            double lane;
            do {
                String lane = sc.nextLine();
                try {
                    lane = Double.parseDouble(lane);
                    if (lanes.get(lane) == null) {
                        lanes.put(lane, new Item(name, lane));
                        break;
                    } else {
                        System.out.println("Lane number already chosen.");
                    }
                } catch (NumberFormatException e) {
                    System.out.println("Please enter a valid lane number.");
                }
           } while (true);
       } while (sc.nextLine().equalsIgnoreCase("y"));
   }

    return lanes;
}