Question

我对如何在开关盒内执行几项检查有疑问？在情况2中，我需要做几次检查，但是添加第二个if块，我的应用程序什么也不做，只是挂起了。我怎么了？

BufferedReader inputCommand = new BufferedReader(new InputStreamReader(System.in));

        while (true) {
                    System.out.println("Instruction:");
                    System.out.println();
                    System.out.println("1 -- Show all product at the store");
                    System.out.println("2 -- Add the product at the client basket");
                    System.out.println("3 -- Show client basket");
                    System.out.println();
                    switch (inputCommand.readLine()) {
                        case "1":
                            basketCommand.get();
                            System.out.println();
                            break;
                        case "2":
                            System.out.println();
                            System.out.println("Select product to add into your basket");
                            if (inputCommand.readLine().equals("su")){
                                basketCommand.addIntoBasket(productContainer.productList.get("su"));
                            }
                            if (inputCommand.readLine().equals("an")){
                                basketCommand.addIntoBasket(productContainer.productList.get("an"));
                            }
                            break;
    }

Answer 1

在第二个case语句中，您应该仅读取下一个输入一次：

{
      "type": "Microsoft.Resources/deployments",
      "name": "SolutionDeployment",
      "apiVersion": "2017-05-10",
      "resourceGroup": "[split(variables('omsWorkspaceId'),'/')[4]]",
      "subscriptionId": "[split(variables('omsWorkspaceId'),'/')[2]]",
      "properties": {
        "mode": "Incremental",
        "template": {
          "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
          "contentVersion": "1.0.0.0",
          "parameters": {},
          "variables": {},
          "resources": [
            {
              "apiVersion": "2017-03-15-preview",
              "type": "Microsoft.OperationsManagement/solutions",
              "location": "[parameters('workspaceRegion')]",
              "name": "[concat('ContainerInsights', '(', split(variables('omsWorkspaceId'),'/')[8], ')')]",
              "properties": {
                "workspaceResourceId": "[variables('omsWorkspaceId')]"
              },
              "plan": {
                "name": "[concat('ContainerInsights', '(', split(variables('omsWorkspaceId'),'/')[8], ')')]",
                "product": "[concat('OMSGallery/', 'ContainerInsights')]",
                "promotionCode": "",
                "publisher": "Microsoft"
              }
            }
          ]
        }
      },
      "dependsOn": [ "[concat('Microsoft.Resources/deployments/', 'WorkspaceDeployment')]" ]
    }

Answer 2

您的第一个if语句吞噬了输入行，因此第二个if语句无任何内容。

只需读取一次就存储该行：

                String readLine = inputCommand.readLine();

                if (readLine.equals("su")){
                    basketCommand.addIntoBasket(productContainer.productList.get("su"));
                }
                else if (readLine.equals("an")){
                    basketCommand.addIntoBasket(productContainer.productList.get("an"));
                }

Answer 3

每次您执行inputCommand.readLine()时，程序都会等待您身边的输入。您无法像本例中那样比较单个输入。最好的方法是将输入保存在变量中，然后执行检查。这样的事情会起作用（未经测试）：

BufferedReader inputCommand = new BufferedReader(new InputStreamReader(System.in));
    while (true) {
                System.out.println("Instruction:");
                System.out.println();
                System.out.println("1 -- Show all product at the store");
                System.out.println("2 -- Add the product at the client basket");
                System.out.println("3 -- Show client basket");
                System.out.println();
                switch (inputCommand.readLine()) {
                    case "1":
                        basketCommand.get();
                        System.out.println();
                        break;
                    case "2":
                        System.out.println();
                        System.out.println("Select product to add into your basket");
                        String input = inputCommand.readLine();
                        if (input.equals("su")){
                            basketCommand.addIntoBasket(productContainer.productList.get("su"));
                        }
                        if (input.equals("an")){
                            basketCommand.addIntoBasket(productContainer.productList.get("an"));
                        }
                        break;
}

Answer 4

如果使用else if替换

case "2":
     System.out.println();
     System.out.println("Select product to add into your basket");
     if (inputCommand.readLine().equals("su")){
        basketCommand.addIntoBasket(productContainer.productList.get("su"));
     }
     else if (inputCommand.readLine().equals("an")){
     basketCommand.addIntoBasket(productContainer.productList.get("an"));
     } 
     break;

Answer 5

我认为这是一个用于学习的基本程序，所以我尝试使其保持简单。

1。别忘了关闭Scanner类。

2。始终将数字输入转换为小写（考虑“ q”与“ Q”的大小写）

3。每次执行“ scanner.nextLine（）”时，程序将停止并等待来自源的输入（在这种情况下，System.in配置为从键盘获取输入）

4.System.out.println将在输入结束时在屏幕上显示“ \ n”，从而导致创建新行，您可以在字符串中使用此char来保存代码行。

完整代码：

import java.util.Scanner;
import java.io.IOException;

public class MyClass {

public static void ShowMenu()
{
      System.out.println("\nInstruction:");
      System.out.println("1 -- Show all product at the store");
      System.out.println("2 -- Add the product at the client basket");
      System.out.println("3 -- Show client basket");
      System.out.println("q -- Quit Program");


}

public static void ProductMenu()
{
      System.out.println("Select product to add into your basket");
      System.out.println();
      System.out.println("ba -- Basketball");
      System.out.println("fi -- Fiat 500");
      System.out.println("ip -- Iphone");
      System.out.println();
}

public static void Exit(Scanner sc) {
    sc.close();
    System.out.println("You've exited the program. goodbye!");
    System.exit(1);
}

public static void main(String args[]) {
    Scanner scanner = new Scanner(System.in);
    String inputCommand = null;

    while (true) {
       ShowMenu();
        switch (inputCommand = scanner.nextLine().toLowerCase()) {
            case "1":
                System.out.println("you entered 1");
                break;
            case "2":
                ProductMenu();
                inputCommand = scanner.nextLine(); //should block

                if (inputCommand.equals("ba")){
                    System.out.println("Basketball added.");
                }
                if (inputCommand.equals("fi")){
                    System.out.println("Fiat 500 added.");


                }
                if (inputCommand.equals("ip")){
                    System.out.println("Iphone added.");

                }
                break;

            case "q":
                Exit(scanner);
                break;
            default:
                System.out.println("Invalid Input");
                break;
        }
   }

}

}

少数，如果在开关盒中

5 个答案: