Arraylist 中每个项目的嵌套 For-each 循环打印答案

【问题标题】：Nested For-each loop printing for every item in ArraylistArraylist 中每个项目的嵌套 For-each 循环打印
【发布时间】：2020-04-22 11:27:47
【问题描述】：

如何修改此代码，使其仅在首先遍历整个列表后才打印出无效消息。我目前的问题是每次没有匹配时它都会打印出这些消息。这不是我打算做的。

public void assignSchedule(Depot depotName) throws Exception {
        String client, driver;
        Boolean exit = false;

        do {
            System.out.printf("%-10s %-10s %10s %n", "Client", "Start Date", "End Date");
            depotName.listWorkSchedulue();
            System.out.print("Enter the client name for the schedule you wish to assign: ");
            client = DepotSystem.input.nextLine();

            for (WorkSchedule ws : depotName.getWorkSchedules())
            {
                if (client.equals(ws.getClient()))
                {
                    System.out.printf("%n%20s%n", "Drivers");
                    depotName.listDrivers();
                    System.out.print("Which Driver do you want to assign this to: ");
                    driver = DepotSystem.input.nextLine();

                    for (Driver drivers : depotName.getDrivers())
                    {
                        if (driver.equals(drivers.userName) && !drivers.assigned)
                        {
                            System.out.printf("%nThe work schedule for client %s is now assigned to %s%n ", client,
                                driver);
                            depotName.getDriver(driver).setSchedule(depotName.getWorkSchedule(client));
                            drivers.setAssigned(true);
                            exit = true;
                        } else if ((!driver.equals(drivers.userName) && drivers.assigned)) {
                            System.out.printf("%nEither not a valid driver or Driver is already assigned a Job.%n");
                        }
                    }
                } else if (!client.equals(ws.getClient())) {
                    System.out.printf("%nPlease enter a valid client.%n");
                }
            }
        } while (!exit);
    }

如果我输入了一个不正确的名字，这个的当前输出如下

Client     Start Date   End Date 
Gary       2020-04-25   2020-04-27
Bob        2020-05-05   2020-05-06
Enter the client name for the schedule you wish to assign: f

Please enter a valid client.

Please enter a valid client.

当我输入错误的名称时，我希望它是这样工作的。

Client     Start Date   End Date 
Gary       2020-04-25   2020-04-27
Bob        2020-05-05   2020-05-06
Enter the client name for the schedule you wish to assign: f

Please enter a valid client.

【问题讨论】：

David - 如果其中一个答案解决了您的问题，您可以通过将其标记为已接受来帮助社区。接受的答案有助于未来的访问者自信地使用该解决方案。查看meta.stackexchange.com/questions/5234/… 了解如何操作。

标签： java foreach

【解决方案1】：

在 for 循环的顶部，您可以执行以下操作来确定是否有任何工作计划包含输入的客户。您随后可以将 depotName.getWorkSchedules() 替换为 clientSchedules 并删除条件 if (client.equals(ws.getClient()))，因为我们知道它们都是具有相同客户端的计划。

请注意，该问题不包含完整的 SSCCE，缺少许多编译所需的基本类，因此可能会出现意外的编译错误。

            List<WorkSchedule> clientSchedules = depotName.getWorkSchedules().stream()
                            .filter(schedule -> client.equals(schedule.getClient()))
                            .collect(Collectors.toList());

            if (clientSchedules.isEmpty()) {
                System.out.printf("%nPlease enter a valid client.%n");
                continue;
            }

【讨论】：

【解决方案2】：

消息Please enter a valid client 应该在for 循环之外打印。按如下方式进行：

public void assignSchedule(Depot depotName) throws Exception {
    String client, driver;
    Boolean exit = false, validClient;

    do {
        System.out.printf("%-10s %-10s %10s %n", "Client", "Start Date", "End Date");
        depotName.listWorkSchedulue();
        System.out.print("Enter the client name for the schedule you wish to assign: ");
        client = DepotSystem.input.nextLine();

        for (WorkSchedule ws : depotName.getWorkSchedules()) {
            if (client.equals(ws.getClient())) {
                validClient = true;
                System.out.printf("%n%20s%n", "Drivers");
                depotName.listDrivers();
                System.out.print("Which Driver do you want to assign this to: ");
                driver = DepotSystem.input.nextLine();

                for (Driver drivers : depotName.getDrivers()) {
                    if (driver.equals(drivers.userName) && !drivers.assigned) {
                        System.out.printf("%nThe work schedule for client %s is now assigned to %s%n ", client,
                                driver);
                        depotName.getDriver(driver).setSchedule(depotName.getWorkSchedule(client));
                        drivers.setAssigned(true);
                        exit = true;
                    } else if ((!driver.equals(drivers.userName) && drivers.assigned)) {
                        System.out.printf("%nEither not a valid driver or Driver is already assigned a Job.%n");
                    }
                }
            } else {
                validClient = false;
            }
        }
        if (!validClient) {
            System.out.printf("%nPlease enter a valid client.%n");
        }
    } while (!exit);
}

【讨论】：

【解决方案3】：

在循环外声明一个布尔值并将其设置为 else if 条件，并在 else if 中检查此布尔值，类似于

 else if (condition && !booleanVariable) {
          System.out.printf("%nPlease enter a valid client.%n");
           booleanVariable = true;
           }

【讨论】：

那么 printf 行应该不再在这里了。